Genetics Answers

For a non-human organism with somatic cells that have 20 chromosomes, indicate the number of
a. chromatids in the G2 phase.
b. chromosomes during prophase of mitosis.
c. synapsed homologous pairs in metaphase I.
d. chromatids in anaphase of mitosis.
e. telomeres in the G0 phase.

select and support the most appropriate response & explain why each of the incorrect statements is eliminated

3. Meiosis in an oocyte
a. creates 4 cells that are identical in size
b. results in qualitatively genetically different meiotic products
c. has an equational division in M I
d. segregates homologous chromosomes in M II
e. creates new allele combinations, along non-sister chromatids, during telophase I

5. Two genetically identical organisms express slightly different phenotypes for a given trait when
raised in different environments. This is an indication that
a. environmental components have a large effect on the expression of the phenotype
b. this phenotype is not multifactorial
c. the trait is determined by a single gene
d. the environment is equally important to the phenotype as the genotype
e. the phenotype is multifactorial but the genotype strongly influences the phenotype

Given the following information about the inheritance of characteristics in pea plants, answer the questions below:
Y (yellow) is dominant to y (green)
R (round) is dominant to r (wrinkled)
B (bitter) is dominant to b (sweet)
S (smooth) is dominant to s (hairy)
L (long pod) shows incomplete dominance to 1 (short pod) (Ll is medium in length)
Given this cross: (P1) Yy Rr Bb SS Ll (male) x yy RR Bb Ss Ll (female)
a. How many different gametes can be formed by the female plant?
b. How many different genotypes are possible in the F1 offspring?
c. How many different phenotypes are possible in the F1 offspring?
d. What percent of the F1 individuals will be
green, bitter, and smooth _______________
hairy, medium, and sweet ______________
round, bitter, and long _________________

Explain how recessive traits or illnesses can result from a loss of function, whereas dominant traits can result from a gain of function.

How many max. tRNA an mRNA can have during translation?
A- 1
B- 2
C- 3
D- 4
Reason?

. In Drosophila melanogaster, there are dominant alleles for gray-body colour and normal wings. The recessive alleles of these two genes result in black body colour and vestigial wings respectively. Flies homozygous for gray body and normal wings were crossed with flies that had black bodies and vestigial wings. Write down this cross. The F1 progeny were then test-crossed, with the following results:
Gray body, normal wings 236
Black body, vestigial wings 253
Gray body, vestigial wings 50
Black body, normal wings 61

a. Write down the genotype for each phenotype. Would you say that these two genes are linked?
b. If so, how many units apart are they on the chromosome?

3. The cross-over frequency between linked genes A and B is 40%; between B and C, 20%; between C and D, 10%; between C and A, 20%, between D and B, 10%. What is the sequence of the genes on the chromosome?