Lecture 20: meiosis and inheritance of traits Flashcards
homologous
two of the same alleles for the gene
-AA or aa, a’a’ or a”a”
heterozygous
two different alleles for the gene
-Aa or aa’ or Aa’ or Aa” or aa”
multiple alleles exist in the rabbit population at the locus for coat color. How many alleles for coat color does an individual rabbit have?
2
males are more often affected by sex-linked traits than females because
males have only one x chromosome
X-inactivation
only one x is expressed in the cell
XX mosaic
some cell expresses the maternal X and other the pattern X
an inactivated x is normally found in the nucleus of which kind of human cell
somatic cells of a female only
female calico cats are XX for two different color alleles. Can male tortoise shell cat exist?
rarely, if the male has 2 x’s and 1 y: XXY
three mechanisms of meiosis and fertilization that contribute to genetic variation
- crossing over
- random alignment of homologous pairs
- random fertilization
result of crossing over
4 unique chromatids on homologous chromatids
crossing over
increases genetic diversity
assume that an animal has a diploid chromosome number of ten (2n=10)
a. how many chromosomes would it have in a somatic cell?
b. how many chromosomes would be present in a cell at the beginning of meiosis 1?
c. how many chromatids would be present at the beginning of meiosis 1?
d. how many chromosomes would be present in each gamete?
10, 10, 20, 5
assume that a plant has a tetraploid chromosome number of 20 (4N= 20)
a. how many chromosomes would it have in a somatic cell?
b. how many chromosomes would be present in a cell at the beginning of meiosis 1?
c. how many chromatids would be present in the cell at the beginning of meiosis I?
d. how many chromosomes would be present in each gamete?
e. is the gamete 1N 2N or 4N?
f. how many different kinds of chromosomes are there(n=)?
20, 20, 40, 10, 2N, 5
meiosis 1
from 1 cell (2n=8) to two cells (n=4)
end of meiosis 1
two cells each n=4
