16 Genetic Crosses and Heredity

Question 1

Define gametes

Answer 1

Haploid cells capable of fusion

Question 2

Define fertilisation

Answer 2

Union of two gametes to form a single cell called a zygote

Question 3

Define alleles

Answer 3

Alternative form of a gene
Located at the same position (locus) on similar chromosomes
Eg. Eye colour

Question 4

Define locus

Answer 4

A genes position on a chromosome

Question 5

What does dominant mean

Answer 5

The allele prevents the recessive allele from being expresssed

Question 6

What does recessive mean

Answer 6

The allele is prevented from being expressed by a dominant allele

Question 7

What does genotype mean

Answer 7

The genetic make-up of an organism

Question 8

What does phenotype mean

Answer 8

The physical make up/appearance of a gene

Question 9

What are genes in relation to phenotype

Answer 9

Genes are the instructions to the cell that help to produce the phenotype

Question 10

Example of genotype and its phenotype

Answer 10

BB + bb = Genotype of parent
B + b= Genotype of gamete
Bb= Genotype of offspring
Black=Phenotype of offspring

Question 11

What is progency

Answer 11

refers to offspring that are produced

Question 12

What does homozygous mean

Answer 12

Means that two alleles are identical

Question 13

What does Heterozygous mean

Answer 13

Means that two alleles are different

Question 14

Using B and b show what Homozygous dominant and homozygous recesive are

Answer 14

Homozygous dominant= BB
Homozygous recessive= bb

Question 15

Whats another name for homozygous

Answer 15

Pure breeding

Question 16

What is a punnett square

Answer 16

Grid used to show the ratio of the genotypes of tje progency in a genetic cross

Question 17

What does incomplete dominance mean

Answer 17

Neither allele is dominant or recessive with respect to the other.
Both alleles are equally expressed in the heterozygous genotype to produce an intermediate phenotype

Question 18

Give an example of incomplete dominanxe (words)

Answer 18

Shorthorn cattle
Genotype RR =red fur
Genotype rr = white fur
Heterozygous condition Rr = Patches of both

Question 19

What is a pedigree

Answer 19

Diagram showing the genetic history of a group of related individuals

Question 20

What is the two sex chromosomes in a MALE

Answer 20

Xy

Question 21

What is the two sex chromosomes in a MALE

Answer 21

XY

Question 22

What are the two sex chromosomes in a female

Answer 22

XX

Question 23

Name one other species where the pattern of sex determination is reverse in humans

Answer 23

Butterflies,moths,birds
Male has XX female has XY

Question 24

Which sex chromosome is longer

Answer 24

X

Question 25

What is Greg Mendels first law called

Answer 25

The law of segregation

Question 26

What is greg mendels second law called

Answer 26

The law of independent assortment

Question 27

What are autosomes

Answer 27

Chromosomes that do not determine sexuality

Question 28

What plants did gregor mendel study

Answer 28

Pea plants

Question 29

What does mendels first law (the law of segregation) state

Answer 29

-Inherited trated are controlled by two alleles -The alleles separate at gamete formation, with each gamete having only one allele

Question 30

What does Mendels second law (the law of independent assortment) state

Answer 30

It states that When gametes are formed… either of a pair of alleles… is equally likely… to combine with either of another pair of alleles

Question 31

What is a monohybrid cross

Answer 31

Involves the study of only one characteristic

Question 32

What is a dihybrid cross

Answer 32

Involves study of two characteristics

Question 33

How many characteristics did mendel study in peas

Answer 33

7

Question 34

Example of law of segregation

Answer 34

The height of a plant is controlled by a pair of alleles Plant T=Tall t=small When gametes are formed only one allele can enter each gamete, the alleles have to separate

Question 35

Chromosomal basis of mendels forst law

Answer 35

Diploid organisms chromosomes occur in matching pairs called homologus pairs Pairs of alleles occupy the same position (locus) on a homologus pair **During meiosis, homologus chromosomes separate and go into different cells As a result pairs of alleles also separate**

Question 36

Give an example of a monohybrid cross and explain why its monohybrid

Answer 36

Eye colour Seed shape Coat colour Each characteristic can display two variations/phenotypes

Question 37

Give an example of a dihybrid cross and explain why its dihybrid

Answer 37

Plant size **AND** pod colour (green or yellow)

Question 38

What does the law of independent assortment mean example (just read it x)

Answer 38

In an organism with the genotype AaBb, either of the As can combine with either of the Bs to form gametes

Question 39

Chromosomal basis of mendels second law

Answer 39

At gamete formation either of a pair of homologous chromosomes .. is equally likely .. to combine with either chromosome of a second homologous pair.

Question 40

Define selfing

Answer 40

Selfing is when you cross a genotype with the same genotype

Question 41

Define linkage

Answer 41

means the genes are located on the same chromosome

Question 42

Define sex linkage

Answer 42

When a gene is carried on a sex chromosome (X or Y)

Question 43

Which sex chromosome carries the most genes

Answer 43

X

Question 44

which gender suffers more from sex linked characteristics

Answer 44

Male

Question 45

Name some sex linked characteristics

Answer 45

Colour Blindness Haemophilia Duchenne Muscular Dystrophy Eye colour in Drosophila (fruit fly)

Question 46

Where is non nuclear DNA found

Answer 46

In chloroplasts and mitochondria

Question 47

What gender is Non nuclear DNA apssed on from by

Answer 47

Female

Question 48

What does non Nuclear DNA allow

Answer 48

Allows organelles to reproduce independently of the cell

Question 49

Which famous scientist is regarded as the father of genetics

Answer 49

Gregor Mendel

Question 50

State the law of segregation

Answer 50

Characteristics are governed by a pair of factors (genes). These factors separate at gamete formation and each gamete receives only one of the pair. At fertilisation a pair of factors is reestablished for each characteristic.