one of two alternate forms of a gene that can have the same locus (location) on homologous chromosomes and are responsible for alternative traits
having two different alleles for a trait (ex. Tt)
having two identical alleles for a trait (ex. TT)
An organism with a dominant allele for a particular form of a trait will always exhibit that form of the trait. (ex. Bb ---The big B would be dominant
the allele that will only exert its effects if no dominant allele is present (2 blonde alleles produce blonde hair)
the particular alleles at specified loci present in an organism ex. Bb or BB or bb
physical characteristics of an organism ex. brown eyes
one allele is not completely dominant over the other allele
ex. B would be the dominant allele in Bb
diploid chromosomal number
the chromosomal number characteristic of an organism, symbolized as 2n: twice the chromosomnal number (n) of the gamete, in humans 2n= 46
Diploid number =
46 (23 pairs of homologous chromosomes)
1 pair of sex chromosomes determines what?
the genetic sex (XX = female, XY = male)
22 pairs of autosomes guide expression what?
of most other traits
the diploid chromosomal complement, typically shown as homologous chromosome pairs arranged from longest to shortest (x and y are arranged by size rather than paired)
the complete set of chromosomes derived from one parent (the haploid genome): or the two sets of chromosomes ex one set from the egg and one set from the sperm
genetic (DNA) makeup; two sets of genetic instructions (maternal and paternal)
What is SS, when it comes to sickle cell?
normal Hb is made
what is Ss, when it comes to sickle cell
sickle-cell trait (both aberrant and normal Hb are made); can suffer a sickle-cell crisis under prolonged reduction in blood O2)
what is ss, when it comes to sickle cell?
sickle-cell anemia (only aberrant Hb is made; more susceptible to sickle-cell crisis)
What is the Punnett square used for?
predicts the possible gene combinations resulting from the mating of parents of known genotypes
formation of gametes (sex or germ cells)
independent assortment of chromosomes
during gametogenisis maternal and paternal chromosomes are randomly distributed to daughter cells, the two alleles of each pair are segregated and distributed independently
when genes on the same chromosome are linked, the genes crossover forming a chiasma and exchange segments so that the recombinant chromosomes have mixed contributions from each parent
a single egg released from the mother is fertilized by one of the trillions of sperm released from the father
reflects the interaction of dominant and recessive allele
used to predict the possible gene combinations resulting from the mating of parents of known genotypes
occurs when both parents have a recessive gene
as in sickle cell anemia ss
multiple allele inheritance (co dominance)
when two genes exhibit more than two forms - such as ABO blood typing
inherited traits determined by genes on the sex chromosome
X linked traits are usually passed on from mother to son
many phenotypes depend on several gene pairs at different locations acting in tandem- which results in continuous, or quantitive, phenotypic variations between two extremes and explains many human characteristics, such as skin color, height, metabolic rate and intelligence
environmentally produced phenotypes mimic conditions which may be caused by genetic mutations (permanent transmissible changes in the DNA)this also occurs as an effect of poor nutrition and drug use (thalidomide babies - that ended up with flipper like appendages)
IA IA or IA i
IB IB or IB i
newborns are screened for a number of anatomical disorders - congenital hip dysplasia, imperforate anus, PKU, and other metabolic disorders - thes tests are mandated by law in many states
Huntington's disease is a disorder passed down through families in which nerve cells in certain parts of the brain waste away, or degenerate.
Huntington's disease is caused by a genetic defect on chromosome 4.
trisomy 21 - a chromosome abnormality with a high incidence in children of older mothers (35 and older)
traces a genetic trait through several generations and helps predict the future
Fetal testing when there is a known genetic disorder - fluid in the amniotic sac is tested through the mothers abdominal wall
chorionic villus sampling - suctions off bits of the chorionic villi from the placenta for examination
human gene therapy
replacing a defective gene with a normal version -
the branch of biology that studies heredity and variation in organisms
(genetics) an organism or cell having two sets of chromosomes or twice the haploid number
(genetics) an organism or cell having only one complete set of chromosomes
diploid number =
46 - 23 pairs of homlogous chromosomes
So glad your using my cards - I hope they help, pay it forward and help someone else
So glad your using my cards - I hope they help, pay it forward and help someone else
the appearance of the chromosomal makeup of a somatic cell in an individual or species (including the number and arrangement and size and structure of the chromosomes)
genetic DNA make up - two sets of genetic instructions (maternal and paternal)
from the mother
from the father
matched genes at the same location on homologous chromosomes
term used to refer to an organism that has two identical alleles for a particular trait
term used to refer to an organism that has two different alleles for the same trait
an allele that masks or suppresses its (recessive) partner
the genetic make up ex. BB
the way the genotype is expressed ex. brown eyes
what are the sexual sources of genetic variation
1. independent assortment of chromosomes
2. crossover of homologues
3. random fertilization of eggs by sperm
the development and maturation of sex cells through meiosis
results in 2 haploid daughter cells with half the number of chromosomes as the original cell, the daughter cells have a set of chromosomes and alleles that are different from each other and from the original diploid cell
What happens during segregation and independant assortment
gametogenesis, maternal and paternal chromosomes are randomly distributed to daughter cells, the two alleles of each pair are segregated during meiosis 1, alleles on different pairs of homlogous chromosomes are distributed independently
What is meant by crossover and genetic recombination
genes on the same chromosome are linked, chromosomes can cross over, forming a chiasma, and exchange segments, these recombinant chromosomes have mixed contributions from each parent
an intersection or crossing of two tracts in the form of the letter X
A chromosome created when crossing over combines the DNA from two parents into a single chromosome.
source of genetic variation caused by the unlimited number of possible sperm & egg combinations
an offspring represents one out of 72 trillion zygote possibilities, how is this made possible?
because of independent assortment and random fertilization
how are most traits determined
by multiple alleles or by the interaction of several gene pairs
types of inheritance include (6)
dominant- recessive inheritance
mutiple allele inheritance (co dominance)
sex linked inheritance
dominant- recessive inheritance
reflects the interaction of dominant and recessive alleles
what does the punnett square do
predicts the possible gene cobinations resulting from the mating of parents of known genotypes
a dominant allele is represented by what?
a capitol letter
One allele can mask the other allele
Heterozygote has a phenotype that is intermediate between the homozygous dominant and recessive phenotypes
Blood types are an example of a trait expressed this way
Traits that depend on several different genes
One form is Y-linked, and the other is X-linked
An alternative gene form
The set of all genes
The actual genetic makeup
Two identical alleles for a gene
The expression of the genes in form (for example, skin color)
What is the chance the offspring will possess these traits or diseases?Albinism, if both parents are heterozygous for the albino gene
What is the chance the offspring will possess these traits or diseases? Huntington's, if one parent is heterozygous for the Huntington's gene
What is the chance the offspring will possess these traits or diseases? Sickle-cell anemia, if one parent is heterozygous for the sickle-cell gene
Polygenic - what type of inheritance (phenotype) occcurs
Multiple-allele - what type of inheritance (phenotype) occcurs
Dominant-recessive -what type of inheritance (phenotype) occcurs
Sex-linked -what type of inheritance (phenotype) occcurs
A cell from a person with trisomy 21 (Down Syndrome) contains _____.
Abnormal chromosome number
A sperm cell is produced by _____.
A blastocyst is produced by _____.
An ovum contains, how many chromosomes?
A zygote contains, how many chromosomes?
What will the offspring's blood type be if Mother is type O, and father is type A
Type A or type O
What will the offspring's blood type be if Mother is type AB, and father is type O
Type A or type B
What will the offspring's blood type be if Mother is type B, and father is type AB.
Type A, type B, or type AB
What will the offspring's blood type be if Mother is type O, and father is type O
Type O only
Alternative forms of genes are called:
Alternative forms of genes are called alleles. Many alleles are either dominant or recessive.
Humans have ____ pairs of chromosomes.
a. 23 b. 46 c.12 d.55 e.60
23 Humans have 23 pairs of chromosomes. Only the egg and sperm have 23 single chromosomes.
What type of allele will be expressed if both dominant and recessive alleles are present for a given trait?
a. Autosomal b. Recessive c. Somatic d. Segregated e. Dominant
Dominant alleles will be expressed in the heterozygous or homozygous state.
Which process listed below separates linked genes during meiosis?
a. Phenotypic plasticity b. Allelic differentiation c. Chiasma, or crossing over d. Sexual differentiation e. Genomic restructuring
Chiasma, or crossing over
Chiasma, or crossing over, separates linked genes during meiosis and increases genetic variation in the offspring.
The form of inheritance in which the heterozygous state is expressed as an intermediate is:
a dominant-recessive inheritance.b incomplete dominance. c multiple-allele inheritance. d polygenic inheritance. e sex-linked inheritance.
In incomplete dominance, the heterozygous state is expressed as an intermediate.
person who inherits the A and the O blood type alleles will possess which blood type?
e Cannot be determined
The A blood type allele is dominant and the O blood type allele is recessive. In the heterozygous state, the O blood type allele is NOT expressed.
Males tend to inherit more sex-linked conditions because:
a. they have two Y chromosomes.
b. there is no corresponding alleles on their X chromosomes.
c. they have more chromosomes than females.
d. there is no corresponding allele on their Y chromosomes.
e. they have two X chromosomes.
there is no corresponding allele on their Y chromosomes.
Males tend to inherit more sex-linked conditions because any defect in the X chromosome (from the mother) has no counterpart on the Y chromosome.
A change in the genetic structure of a gene is called:
A change in the genetic structure of a gene is called mutation. This change might affect the functioning of a gene.
Extrachromosomal inheritance involves genes passed on by the mother's:
b Golgi bodies.
c smooth ER.
Extrachromosomal inheritance involves genes passed on by the mother's mitochondria. Mutant forms of mitochondrial genes cause some rare genetic diseases.
The most common form of fetal testing is:
a somatic visualization.
b chorionic villi sampling.
c teratogenic sampling.
d gene therapy.
The most common form of fetal testing is amniocentesis, in which fetal cells extracted from the amniotic fluid are tested for abnormalities.
The expression of genes is called the:
The actual genetic makeup is called the genotype, but the expression of the genotype is the phenotype.
Traits that display continuous phenotypic variation are usually determined by this form of inheritance.
a Dominant-recessive inheritance
b Incomplete dominance
c Sex-linked inheritance
d Polygenic inheritance
e Multiple-allele inheritance
Traits that display continuous phenotypic variation are usually determined by polygenic inheritance.
What is the probability of having a child with a recessive trait if both parents are heterozygous for the trait?
Each parent has a 50% chance of donating the recessive allele to the baby. 50% × 50% = 25%.
A type of treatment useful in correcting single-gene disorders is:
a genetic dysplasia.
b somatic recombination.
c gene therapy.
e chorionic villi sampling.
The most common approach involves transferring a correct gene via a virus to the affected cells.
Heterozygous individuals that can pass on recessive, abnormal conditions are referred to as:
b phenotypically challenged.
c deleterious donators.
e recessively compromised.
While they don't have the disease, they can pass, or "carry," it to their offspring.
Genes that are located on the same chromosome are said to be:
Genes that are located on the same chromosome are said to be linked. They are inherited together unless they are broken up during the crossing over process.
In the human blood type AB, the alleles are:
In the human blood type AB, the alleles are codominant.
Which of the following disorders is NOT inherited as simple recessive traits?
a Cystic fibrosis
c Tay-Sachs disease
d Down syndrome
Down syndrome is a chromosome abnormality.
If a male inherits a sex-linked gene for color blindness:
a it will never be expressed.
b it will be expressed only if two copies are present.
c it will only be expressed 25% of the time.
d it will always be expressed
it will always be expressed.
Males always express X-linked genes.
The appearance of freckles is considered:
a the genome.
b the phenotype.
c the genotype.
d sex linked.
The appearance of freckles is considered the phenotype.
A person without a Y chromosome will:
a show both male and female characteristics.
b always show female characteristics.
c always show male characteristics.
d be sterile, but show male characteristics.
always show female characteristics.
The Y chromosome has the SRY gene, which is necessary for male characteristics to develop.
The 46 chromosomes of a zygote come from
a the egg.
b the sperm.
c the mother and the father.
the mother and the father.
Both parents contribute equally to the DNA content.
A karyotype is a complete:
a display of autosomes.
b haploid complement display of chromosomes.
c display of sex hormones.
d diploid complement display of homologous chromosome pairs.
diploid complement display of homologous chromosome pairs.
A karyotype is a complete diploid complement display of homologous chromosome pairs.
Any two matched genes that are __________ are called alleles.
a at the same locus on homologous chromosomes
b found only in the mother
c at the same position on the sex chromosomes
d found only on autosomes
at the same locus on homologous chromosomes
Alleles are genes that are at the same locus on homologous chromosomes whether they are autosomes or sex chromosomes.
If the allele for brown hair was represented as "B": would mean that
a the gene for brown hair is carried on the maternal chromosome.
b the gene for brown hair is carried on the paternal chromosome.
c brown hair was a recessive trait.
d brown hair was a dominant trait.
brown hair was a dominant trait.The representation of the brown hair gene by "B" means it is a dominant trait.
Most human traits are determined by:
a a single allele.
b nutrition during infancy.
c a single pair of genes.
d multiple alleles.
Most human traits are determined by multiple alleles
Heterozygous parents who have had one child with a recessive disease will have a ___ chance of having their second child being born with the same recessive disease.
Heterozygous parents who have had one child with a recessive disease will have a 25% chance of having their second child being born with the same recessive disease.
A phenocopy occurs when:
a two individuals have exactly the same genetic composition.
b an individual carries the same copy of the gene at both alleles.
c an individual develops a phenotype that is similar to a condition caused by mutant genes but is actually caused by environmental factors and does not have a genetic basis.
an individual develops a phenotype that is similar to a condition caused by mutant genes but is actually caused by environmental factors and does not have a genetic basis.
In females, one of the X chromosomes is inactivated by:
a environmental factors.
b enzymes coded for by mitochondrial DNA.
c epigenetic markers.
d the number of dominant genes present on each X chromosome
In females, epigenetic markers inactivate one of the X chromosomes.
True or False Gregory Mendel worked out the basic modes of inheritance during the mid-1900s
False Mendel worked in the mid-1800s.
True or False All traits are either dominant or recessive.
False There are other modes of inheritance, such as sex-linked inheritance.
True or False It is possible to detect heterozygous carriers of Tay-Sachs, cystic fibrosis, and sickle cell anemia
True Blood tests and DNA probes are used to detect carriers for these diseases.
True or False Chorionic villi sampling is performed earlier in gestation than is amniocentesis.
True Chorionic villi sampling is performed after 8 weeks, and amniocentesis is performed after 14 weeks.
True or False Genes located further apart from one another on a chromosome have a greater chance of crossing over.
True Genes located nearer one another have a greater chance of staying together.
True or False Females inherit more sex-linked traits than males
False Males inherit more sex-linked traits, because they don't have corresponding regions on their Y chromosome.
True or False Continuous phenotypic variation is characteristic of incomplete dominance or intermediate inheritance
False Continuous variation occurs with polygenic inheritance.
True or False Genomic imprinting confers different effects and phenotypes on maternal and paternal genes.
True Imprinting involves methylation of certain genes during gametogenesis.
True or False Environmental factors may influence the expression of the genotype.
True Freckles do NOT appear if skin is NOT exposed to sunlight.
True or False Genes located on the same chromosome are always inherited together
False Genes are linked if they are on the same chromosome, but may be separated by crossing over that occurs during meiosis I.
True or False The two sex chromosomes are considered autosomes.
False They are considered sex chromosomes; the X and Y chromosomes have different genes.
True or False A person with blood type A (AO genotype) will be considered heterozygous for the trait of blood type
True One allele is A, and the other allele is O. O is recessive to A and will NOT be expressed. Alleles are different.
True or False Genetic information is carried on DNA.
True DNA contains genes.
True or False The total number of chromosomes found within a human zygote is 23.
False A zygote receives 23 chromosomes from each gamete, and, therefore, has 46 chromosomes.
why are autosomal dominent disorders uncommon
because many are lethal and result in death before reproductive age
How is huntingtons disease caused
by a delayed action gene
sickling gene SS
normal HB is made
sickling gene Ss
sickle cell traint - both aberrant and normal Hb are made can suffer a sickle crisis under prolonged reduction in blood O2
Sickling gene ss
sickle cell anemia (only aberrant Hb is made, more susceptible to sickle cell crisis
alleles for type A Blood
IA IA or IA i
allele for type B Blood
IB IB or IB i
allele for type AB blood
allele for type O blood
sex linked inheritance
inherited traits determined by genes on the sex chromosomes
X chromosomes bare 2500 genes - many are for what
Y chromosomes carry how many genes
X linked genes are (3)
1. found only on the X chromosome
2. typically passed from mothers to sons (eg hemphillia or red green color blindness)
3. never masked or damped in males (no Y counterpart)
polygene inheritance depends on what
several different gene pairs at different locations acting in tandem
polygene inheritance results in what
continuous phenotypic variation between two extremes
examples in polygene inheritance
skin color, eye color, height
environmentally produced phenotypes that mimic conditions caused by genetic mutation
environmental factors can influence genetic expression after birth such as what? (2)
poor nutrition can affect brain growth, body development, and height
childhood hormonal deficits can lead to abnormal skeletal growth and proportions
what are some of the things that newborns are screened for
congenital hip dysplasia, imperforate anus, PKU and other metabolic disorders,
why would a woman ove rthe age of 35 be tested during prenancy? if it were her first pregnancy?
to see if the baby has trisomy 21 - which is Down syndrome
what are the two major avenues for identifying carriers of genes?
pedigrees and blood tests
what do pedigrees trace?
a particular genetic trait through several generations - helps predict the future
what do blood test and DNA probes detect?
the presence of unexpressed recessive genes
what diseases can be identified from pedigrees and blood tests?
tay Sachs and Cystic fibrosis
when is fetal testing used?
when there is a known genetic disorder
what is amniocentesis
amnioitic fluid is withdrawn after the 14th week and fluid and cells are examined for genetic abnormalities
what is CVS
chronic villus sampling - chronic villi are sampled and karyotyped for genetic abnormalities
what is human gene therapy
genetic engineering has the potential to replace a defective gene, defective cells can be infected with a genetically engineered virus containing a functional gene, the patients cells can be directly injected with corrected DNA