Genetic basis of variation

Question 1

Explain the term locus.

Answer 1

a specific gene position on the chromosome

Question 2

Explain the term allele.

Answer 2

alternative forms of the same gene and occupy the same locus of a pair of homologous chromosome

Question 3

Explain the term dominant.

Answer 3

condition where the effect of only one allele is apparent in the phenotype even in the presence of an alternative allele

…

Question 4

Explain the term recessive.

Answer 4

condition where the effect of one gene is apparant in the diploid organism only in the presence of another identical allele

…

Question 5

Explain the term co-dominant.

Answer 5

each allele of the pair is expressed equally

patches of both colour

Question 6

Explain the term incomplete dominance.

Answer 6

phenotype of the heterozygote is distinct from and often intermediate to the phenotypes of the homozygotes

red+blue = purple

Question 7

Explain the term homozygous.

Answer 7

2 identical alleles at a given gene locus

Question 8

Explain the term heterozygous.

Answer 8

2 different alles at a given gene locus

Question 9

Explain the term phenotype.

Answer 9

characteristics of an organism that results from the interaction between its genotype and the environment in which development occurs

Question 10

Explain the term genotype.

Answer 10

genetic constitution of an organism with respect to the alleles under consideration

Question 11

Explain the term linkage.

Answer 11

when two or more genes are found on the same chromosome, they are known as linked genes with respect to each other

Question 12

What are the different modes of inheritance?

(8?)

Answer 12

1. dominant-recessive
2. incomplete dominance
3. co-dominance
4. multiple alleles
5. sex linkage
6. autosomal linkage
7. epistasis
8. polygenic inheritance

Question 13

What is the Mendelian Genetics?

Answer 13

look at characteristics that varied between two distinct alternatives
1. alternative forms of the genes, alleles
2. for each characteristic, an organism inherits two alleles - one from each parent
3. if the two alleles at the locus differ, then one (dominant allele) determines the organisms’ appearance the other allele (recessive allele) has no noticeable effect on the organism’s appearnce.
4. the two alleles for a hertitable characteristic segregate during gamete formation (anaphase I meiosis) - Mendel’s first law the principle of segregation.

Question 14

Which modes of inheritance follow Mendelian genetics?

Answer 14

1. monohybrid cross
2. simple dihybrid cross

Question 15

Which modes of inheritance does NOT follow Mendelian genetics?

Answer 15

1. co-dominance
2. incomplete dominance
3. sex linkage
4. multiple alleles
5. linked genes
6. epistasis

Question 16

How many chromosomes do we have in out body?

Answer 16

23 pairs

Question 17

What affects the frequency when crossing over occurs btw 2 linked genes?

Answer 17

the distance between the linked genes

Question 18

What are linked genes?

Answer 18

genes on the same chromosome -> do not show independent assortment and fail to produce mendel’s expected ratio

Question 19

What is epistasis?

Answer 19

• a form of gene interaction
• both genes control one characteristic
• if one gene locus masks the expression of a second gene, the first locus is epistasic to the second and the second is hypostatic to the first

Question 20

What are the different types of epistasis?

Answer 20

1. recessive
2. duplicate recessive
3. dominant
4. duplicate dominant

Question 21

What is recessive epistasis?

Answer 21

the expression of either phenotype depends on the presence of the dominant allele

Question 22

Name an example of recessive epistasis.

Question 23

What is duplicate recessive epistatic?

Question 24

Name an example of duplicate recessive epistasis.