Heredity

Question 1

diploid number

Answer 1

• The number of chromosomes present in the body cells of a diploid organism.
• 2n

Question 2

haploid component

Answer 2

pertaining to a single set of chromosomes

humans=23

(n)

Question 3

homologous chromosomes

Answer 3

A set of one maternal and one paternal chromosomes that pair up with each other inside a cell during meiosis.

Homologous chromosomes are similiar but not identical. Each carries the same genes in the same order, but the alleles for each trait may not be the same.

Question 4

allele

Answer 4

An allele is a variant form of a gene.

Question 5

heterozygous

Answer 5

A diploid organism is heterozygous at a gene locus when its cells contain two different alleles of a gene.

Question 6

homozygous

Answer 6

Alternative forms of a given gene are called alleles, and they can be dominant or recessive. When an individual has two of the same allele, whether dominant or recessive, they arehomozygous. Heterozygous means having one each of two different alleles.

Question 7

gene

Answer 7

A portion of a DNA molecule that serves as the basic unit of heredity.Genes control the characteristics that an offspring will have by transmitting information in the sequence of nucleotides on short sections of DNA.

Question 8

dominant allele

Answer 8

An allele that expresses its phenotypic effect even when heterozygous with a recessive allele; thus if A is dominant over a, then AA and Aa have the same phenotype.

Question 9

recessive allele

Answer 9

an allele that produces its characteristic phenotype only when its paired allele is identical.

Question 10

genotype

Answer 10

The genetic constitution of an individual organism.

Question 11

phenotype

Answer 11

the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

Question 12

monohybrid cross

Answer 12

A genetic cross between homozygous individuals but with different alleles for a single gene locus of interest.

Question 13

dihybrid cross

Answer 13

In the name “Dihybrid cross”, the “di” indicates that there are two traits involved (e.g. R and Y), the “hybrid” means that each trait has two different alleles (e.g. R and r, or Y and y), and “cross” means that there are two individuals (usually a mother and father) who are combining or “crossing” their genetic information.

The Dihybrid cross is easy to visualize using a Punnett square of dimensions 4 x 4.

Question 14

incomplete dominance

Answer 14

A form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a thirdphenotype in which the expressed physical trait is a combination of the phenotypes of both alleles.

Question 16

autosome

Answer 16

An autosome is a chromosome that is not an allosome (a sex chromosome). Autosomesappear in pairs whose members have the same form but differ from other pairs in a diploid cell, whereas members of an allosome pair may differ from one another and thereby determine sex.

Question 17

sex chromosome

Answer 17

aka allosome

A chromosome involved in the determination of the sex of offspring produced via sexual reproduction. Contrast with autosomes which are not involved in sex determination. Individuals receive one allosome from each of their parents.

Humans have two types of allosomes, X-chromosomes and Y-chromosomes. Females have two X-chromosomes, and males have one X and one Y-chromosome.

Genes on the allosomes are called sex-linked genes because their inheritance and expression patterns differ between males and females.

Question 19

Answer 19

heterozygous

Question 20

Answer 20

homozygous

Question 21

Answer 21

incomplete dominance