DAT bio chapter 7. Heredity P2 Flashcards
nondisjunction
improper segregation of
chromosome pairs during anaphase; it produces
daughter cells with an incorrect number of
chromosomes.
Single nondisjunction of homologous
chromosomes during meiosis I
46 chromosomes in diploid parent cell
→
24, 24, 22, 22 chromosomes in haploid daughter
cells
Single nondisjunction of sister chromatids
during meiosis II
46 chromosomes in diploid parent cell
→
24, 22, 23, 23 chromosomes in haploid daughter
cells
Single nondisjunction of sister chromatids
during mitosis
46 chromosomes in diploid parent cell
→
47, 45 chromosomes in diploid daughter cells
Aneuploidy
abnormal number of
chromosomes in the daughter cells.
examples of aneuploidy
trisomy (3 chromosomes copies) or
monosomy (1 chromosome copies) can occur.
Down syndrome
a trisomy of chromosome #21
each diploid cell has 47 chromosomes total
Turner syndrome is
a monosomy of the X
chromosome in females (each diploid cell has 45
chromosomes total). Affected individuals have
physical abnormalities and sterility
Klinefelter’s syndrome i
is a trisomy of the sex
chromosomes in males, giving them XXY (each
diploid cell has 47 chromosomes total). Individuals
usually have disorders in intellectual, physical, and
reproductive developmen
test-cross pairs what and what
pairs unknown genotype with a homozygous recessive
How do we determine unknown genotype?
looking at the offspring from a test cross
True-breeding organisms are
homozygous for all the traits of interest
What is the F1 generation>
first
generation cross between true-breeding parents
with different alleles. The offspring are all
heterozygous.
What is the F2 generation?
second generation cross between the
heterozygous offspring from the F1 generation.
This is where Mendel’s three laws can be studied
What is a monohybrid cross?
single gene is examined from 2 generations. In the F2 generation, the genotype ratio
(AA:Aa:aa) should be (1:2:1) and the phenotype
ratio (dominant:recessive) should be (3:1).
Dihybrid cross
two genes on separate chromosomes are examined. The phenotype ratio is (9:3:3:1).
single allele
crosses you should memorize
Homozygous x homozygous = 1/1 AA or 1/1 Aa or 1/1 aa 2. Homozygous x heterozygous = ½ AA (or aa) and ½ Aa 3. Heterozygous x heterozygous = ¼ AA, ½ Aa, ¼ aa
What does pedigree charts do?
track inherited traits
over many generations to see inheritance
patterns.
Females are represented by what in pedigree charts
circles
males are represented by what in pedigree charts?
squares
Individuals
affected and unaffected by the trait in question are represented how?
shaded for affected individuals and unaffected individuals are not shaded/
Individuals
affected and unaffected by the trait in question are represented how?
shaded for affected individuals and unaffected individuals are not shaded/
recombinant gametes s
gametes (sex cells) that receive the genetically unique chromatids (new combination of alleles)
non-recombinant
gametes
gametes that receive
parental chromatids (alleles match parent’s
alleles)
Linked genes location
are found close together on the same
chromosome
How do we calculate the distance of linked genes
by looking at recombination
frequencies, we can deduce the relative distance
between these genes.
what is one map unit
chromosomal
distance that would allow 0.01 crossover events
per generation.
Example of map unit
20 map units would mean 0.2
crossover events occur between the two genes per
generation, or that there is a 20% chance of
recombination.
Recombination frequencies of less than 50%
mean what?
two genes are linked
. A random
assortment of unlinked genes have what
50%
recombinant progeny.
what can be drawn out using map units to infer the distance between genes on a chromosome?
linkage maps
a group of genes that are usually
inherited together because they are located in
close proximity to each other
haplotype
haplotype
a group of genes that are usually
inherited together because they are located in
close proximity to each other
Sex-linked traits
come from genes located on the
sex chromosomes
Most sex-linked disorders have
X-chromosome linkage. how many types of sex linked traits are there
three types
X-linked dominant -
- dominant inheritance on
the X chromosome. Any offspring (male or
female) that receive the affected allele will end
up with the disorder
X-linked recessive
recessive inheritance on
the X chromosome. For males, only one
affected allele is needed to cause the disorder.
For females, two affected alleles are needed to
cause the disorder because females have two
X chromosome
Y-linked
inheritance on the Y chromosome.
Can only be passed from father to son. Will
always be expressed whether it is dominant or
recessive because males only have one Y
chromosome.
Genomic imprinting
genes that are
expressed depending on parental origin and are
influenced by epigenetic factors. (different from sex-linked traits because they can
come from autosomal chromosomes (non-sex
chromosomes) as well.)
X-inactivation
process by which one of a
female’s X chromosomes is inactivated, forming a
Barr body and preventing excess transcription.
When can female carrier become an affected individual for a disease?
if her unaffected
X chromosome with a normal wild-type allele is
inactivated, leaving behind a recessive allele that is
not covered up.
What does epigenetics do?
does not involve modifying the
genetic code, but instead the REGULATION of when
genes are expressed. Epigenetic changes are
heritable.
examples of epigenetic changes
DNA methylation - histone acetylation histone de acetylation heterochromatin histone methylation
