genetics

Question 1

Define Homologous Chromosomes

Answer 1

HC are similar in size, shape, gene locus, centromere position, and staining pattern,

have same genes determining certain trait at same loci,

but the gene may be of different alleles

Question 2

define gene locus

Answer 2

Position of gene on chr,

where Alternative form of a gene, (having a different nucleotide sequence) occupies the same locus,

there are diff genes at diff locus

Question 3

define gene

Answer 3

An ordered sequence of DNA nucleotide located at particular locus, on a particular
chr, that encodes for a specifical functional produc

Question 4

Define alleles

Answer 4

Alternative form of a gene, having a different nucleotide sequence

Question 5

define phenotype

Answer 5

Expressed trait of organism due to genotype & environmental influences

Question 6

what makes a gene dominant?

Answer 6

An allele that expresses its phenotype regardless if its homozygous/heterozygous → gene
pdt of dominant allele masks effect of gene product expressed by recessive allele

Question 7

how do you know a gene is recessive?

Answer 7

Allele that is only expressed in homozygous recessive organism

Question 8

define codominance and give an example

Answer 8

When 2 different dominant alleles of the same genes are both equally expressed in heterozygote’s phenotype & influence the phenotype → Red/White flowers (both flowers exist) & AB blood group: IAIB

Question 9

define incomplete dominance and give an example

Answer 9

When phenotype of heterozygous is an intermediate btwn phenotypes of both homozygous for either allele → Pink flowers (Red + White: CRCW= pink)

Question 10

How do you carry out a test cross?

Answer 10

A cross with a homozygous recessive

Question 11

Why do we do a test cross?

Answer 11

To determine whether the subject is homo dom/rec/heterozygous

Question 12

Environment influences organisms. Give an example of the environment influencing the genetics of organism.

Answer 12

Temperature
Fur colour of Himalayan Rabbits:
Cooler body parts → black fur, Warmer body parts → white fur → reduce heat loss → survive better

Food
Diet of honeybees affect their Differentiation:
Larvae of honey bee fed with Royal Jelly → becomes Queen bees

Question 13

Give the outcomes of the following MONOHYBRID crosses:

• Hh x Hh =
• Hh x hh = (test cross)
• hh x hh =
• HH x HH =

Answer 13

• Hh x Hh = 3:1
• Hh x hh = 1:1
• hh x hh = all recessive
• HH x HH = all dominant

Question 14

An organism has 2 gene loci: A and B. Both A and B genes interact to determine the fur type of this organism. What kind of genetics interaction is happening here?

Answer 14

2 genes
1 trait
= epistasis
Gene interaction where a gene at 1 locus affects phenotypic expression of a gene at 2nd locus

Question 15

If you cross a heterozygous for 2 gene loci, what outcome do you expect?

If the outcome is not you predicted, what kind of genetic interaction is happening?

Answer 15

e.g. AaBb x AaBb
= 9:3:3:1

If altered dihybrid ratio = Incomplete Linkage (most of the time)

IF THE RATIO BECOMES MONOHYBRID RATIO e..g 1:1 or 3:1 CONFIRMS COMPLETE* LINKAGE!