genetics: mendelian inheritance SDL

Question 1

define gene

Answer 1

A discreet unit of DNA which codes for a protein

Question 2

define locus

Answer 2

The position of a gene on a chromosome

Question 3

define allele

Answer 3

An alternative form of a gene that produces a distinguishable phenotypic effect

Question 4

define genotype

Answer 4

The alleles contained in an organisms cells

Question 5

define phenotype

Answer 5

The characteristics of an organism determined by its genotype and its environment

Question 6

define homozygous

Answer 6

An organism which possesses 2 identical alleles of the same gene

Question 7

define heterozygous

Answer 7

An organism which possesses 2 different alleles of the same gene

Question 8

define dominant allele

Answer 8

Allele which is always expressed in the phenotype if it is present in the genotype

Question 9

define recessive allele

Answer 9

Allele which is only expressed in the phenotype when the dominant allele is not present

Question 10

define codominance

Answer 10

When both alleles affect the phenotype of a heterozygous individual

Question 11

define F1

Answer 11

First filial generation, the first hybrid offspring of two pure breeding parents

Question 12

define F2

Answer 12

Second filial generation, the offspring from interbreeding the F1 generation

Question 13

what is the law of segregation

Answer 13

Law of segregation: states that the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes

Question 14

what is the law of indipendent assortment

Answer 14

The law of independent assortment states that each pair of alleles segregates independently of each other pair of alleles during gamete formation
- this law only applies to genes on different, non homologous chromosomes
- genes located near each other on the same chromosome tend to be inherited together

Question 15

what are linked genes

Answer 15

Genes located on the same chromosome that tend to be inherited together are called linked genes
- crossing over between linked alleles can produce recombinant individuals

Question 16

what is incomplete dominance

Answer 16

both allels on a gene locus are partially expressed

Question 17

what are epistatic genes

Answer 17

genes that mask or interfere with the effects of other genes

Question 18

what is the difference between incomplete dominance and codominance

Answer 18

Codominance
Both alleles at a gene locus are fully expressed in the phenotype, resulting in two possible phenotypes. This is a heterozygous state, where both phenotypes are partially dominant.
Incomplete dominance
One allele for a trait is not fully expressed over its paired allele, resulting in a third phenotype that is a combination of both alleles. This is a form of intermediate inheritance.
In codominance, no allele can block or mask the expression of the other allele. In incomplete dominance, neither trait is truly dominant over the other, resulting in a blending of the two phenotypes