B4

Question 1

What is the simple definition of a gene

Answer 1

a unit of inheritance located at a particular locus of a chromosome

Question 2

What is the detailed definition of a gene

Answer 2

A specific DNA sequence which codes for RNA + controls a particular characteristic or protein in an organism

Question 3

what is an allele

Answer 3

an alternative form of a gene at a particular gene locus

Question 4

What are alleles responsible for

Answer 4

responsible for determining contrasting traits of the same

character

Question 5

How do alleles occur in different cell types

Answer 5

alleles occur in pairs in a diploid cell but only one is represented in a gamete

Question 6

How do alleles position themselves on homologous chromosomes

Answer 6

they occupy the same relative positions on a pair of homologous chromosome

Question 7

Define phenotype

Answer 7

the physical manifestation of a genetic trait that results from a specific genotype and its interaction with the environment

Question 8

Define genotype

Answer 8

the complete genetic makeup of an organism (commonly referring to the paired alleles)

Question 9

Define heterozygous

Answer 9

condition in which the alleles of a gene pair are different (e.g. Tt)

Question 10

Define homozygous

Answer 10

condition in which the alleles of a gene pair are identical (= true / pure breeding)

• homozygous dominant (e.g. TT)
• homozygous recessive (e.g. tt)

Question 11

What is homozygous dominant

Answer 11

TT

Question 12

What is homozygous recessive

Answer 12

tt

Question 13

Describe the dominant allele

Answer 13

A dominant allele expresses itself and gives the same phenotype in both the homozygous dominant and heterozygous conditions. (masks the influence of the recessive allele)

Question 14

Describe the recessive allele

Answer 14

A recessive allele does not express itself in the heterozygous condition and only expresses itself in the homozygous recessive condition

Question 15

What is the structure of a chromosome

Answer 15

rod-like structure visible in the nucleus during cell division

Question 16

What is a chromosome made up of

Answer 16

made up of deoxyribonucleic acid (DNA)

Question 17

What does DNA contain

Answer 17

DNA carries the hereditary information for making new organisms

Question 18

What might each chromosome carry

Answer 18

each chromosome may carry many genes along its length

Question 19

What is the nucleus in terms of genetics

Answer 19

The nucleus is the site of genetic material/chromosomes/genes in plant and animal cells

Question 20

What is a monohybrid cross

Answer 20

Monohybrid cross: a cross between two pure-breeding organisms

Question 21

What is monohybrid inheritance and how is this character controlled

Answer 21

an inheritance involving only one pair of contrasting traits

• The character is controlled by a single gene (a pair of alleles).

Question 22

What are genetic diagrams used for

Answer 22

used to predict the traits that will be expressed by the offspring (genetic cross)

Question 23

What happens if the trait is dominant on a pedigree

Answer 23

• Unaffected parents should not have affected children.
• Trait should not skip generations – affected individuals must have affected parent(s).
• When an affected individual mates with an unaffected individual, 50% of their offspring should be affected (heterozygous).

Question 24

What happens if the trait is recessive on the pedigree

Answer 24

• If both parents are affected, all children should be affected.
• Unaffected parents can produce affected individuals.
• Trait often skips generations.
*Note: Most phenotypic features are the result of multiple genes rathe

Question 25

What are phenotypic features due to

Answer 25

Most phenotypic features are the result of multiple genes rather than a single gene inheritance