chapter 5 - genetics

Question 1

Define pure breeding

Answer 1

A line of organisms that always produce offspring with the same phenotype when crossed with one another

Question 2

Define filial generation

Answer 2

The successive generation resulting from the genetic cross between two parents

Question 3

Define dominant gene

Answer 3

A dominant gene requires only copy of its allele for it to be expressed in an individual - has the ability to mask a recessive gene so it will not be expressed in the phenotype

Question 4

Define recessive gene

Answer 4

A recessive gene requires two copies of its allele in an individual in order to be expressed in the phenotype - in a heterozygous individual this trait is typically masked by a dominant gene

Question 5

Define allele

Answer 5

On of various versions of the same gene at the same locus which are distinguished by small differences in its DNA sequence

Question 6

Define homozygous

Answer 6

A genotype with two identical alleles for a single gene locus

Question 7

Define trait

Answer 7

A trait is an inheritable characteristic determined by the genotype and expressed as the phenotype

Question 8

Define heterozygous

Answer 8

A genotype with two different alleles for a single gene locus

Question 9

Define incomplete/partial dominance

Answer 9

Incomplete dominance occurs when a heterozygous organism has a phenotype that is intermediate of the phenotype of homozygous individuals (aka the phenotype is expressed as a blend of the homozygous phenotype seen in other organisms). This occurs because neither allele is fully dominant and both contribute to the phenotype partially, an example is the flower petal colours (red and white make pink)

Question 10

Define codominant

Answer 10

When both alleles of a heterozygous organism are expressed in the phenotype. This occurs because both alleles are dominant and are unable to mask one other, so both are expressed in the phenotype. An example is the coat colour of cows, (if dad is white and mom is red, the kid wont be pink or red or white, but have patches of red and white coat)

Question 11

Define segregation

Question 12

Define test cross

Answer 12

A technique used to find the unknown genotype of an organism that is displaying a dominant phenotype (bc if the phenotype showed it was homozygous recessive you wouldnt need a test). The test cross is performed by producing offspring of the organism and a homozygous recessive organism, and the ratio in phenotype determines the unknown genotype (100% dominant phenotype then must be homozygous, 50/50 then must be heterozygous)

Question 13

Define autosomal

Answer 13

When a trait is coded for by a gene located on an autosome (regular chromosome), the trait is autosomal. Autosomal inheritance occurs when a trait found on an autosome is passed on.

Question 14

Define sex-linked

Answer 14

Describes a gene located on a sexosome, and sex-linked traits are inherited on either the X or Y chromosome.

Question 15

Define monohybrid

Answer 15

An organism that is heterozygous for one gene

Question 16

Define dihybrid cross

Answer 16

A cross between two organisms that are heterozygous at two gene loci