Human Genetics chapter 3

Question 0

Dominant trait

Answer 0

The trait expressed in the F1 (or heterozygous) condition.

Question 1

Gene

Answer 1

1. The fundamental unit of heredity and the basic structural and functional unit of genetics
2. A distinct sequence of nucleotides forming part of a chromosome

Question 2

Recessive trait

Answer 2

The trait unexpressed in the F1 but re-expressed in some members of F2 generation.

Question 3

Phenotype

Answer 3

The observable properties of an organism

Question 4

Genotype

Answer 4

The specific genetic constitution of an organism

Question 5

Segregation

Answer 5

1. The separation of members of a gene pair from each other during gamete formation.
2. Defines an allele
3. Organisms inherit one allele from each parent
4. Gametes only carry one allele for each trait
5. Defines differences between dominant and recessive genes

Question 6

Allele

Answer 6

One of the possible alternative forms of a gene, usually distinguished from other alleles by its phenotypic effects.

Question 7

Homozygous

Answer 7

Having identical alleles for one or more genes.

Question 8

Heterozygous

Answer 8

Carrying two different alleles for one or more genes.

Question 9

Independent assortment

Answer 9

1. The random distribution of genes into gametes during meiosis.
2. When genes are inherited they are inherited independently of each other

Question 10

Genetics

Answer 10

The scientific study of heredity

Question 11

Locus

Answer 11

The position occupied by a gene on a chromosome.

Question 12

Pedigree construction

Answer 12

Use of family history to determine how a trait is inherited and to estimate risk factors for family members

Question 13

Pedigree

Answer 13

A diagram listing the members and ancestral relationships in a family;used in the study of human heredity.

Question 14

Proband

Answer 14

First affected family member who seeks medical attention for a genetic disorder.

Question 15

Incomplete dominance

Answer 15

Expression of a phenotype that is intermediate to those of the parents.

Question 16

Codominance

Answer 16

Full phenotypic expression of both members of a gene pair in the heterozygous condition.

Question 17

Multiple alleles

Answer 17

Genes that have more than two alleles.

Question 18

Epistasis

Answer 18

The interaction of two or more non-allelic genes to control a single phenotype.

Question 19

Hybrid cross

Answer 19

homozygous dominant x homozygous recessive

Question 20

Monohybrid cross

Answer 20

examines one gene (e.g. gene for seed shape) 3:1

Question 21

Dihybrid cross

Answer 21

2 genes (e.g genes for seed shape and see color) 9:3:3:1

Question 22

What Mendel knew

Answer 22

1. Mendel had no knowledge of mitosis, meiosis, or chromosomes.
2. By 1900, it became obvious that gene and chromosomes has much in common.
3. Genes: occur in pairs (alleles); members of a gene pair separate from each other during meiosis; members of one gene pair independently assort from other gene pairs during meiosis.
4. Chromosomes: Occur in pairs (homologues); members of a homologous. pair separate from each other during meiosis; members of one chromosome pair independently assort from other chromosome pairs during meiosis.