Topic 3 - Genetics

Question 1

What is sexual reproduction?

Answer 1

Reproduction involving production of gametes by meiosis

Question 2

What happens during sexual reproduction?

Answer 2

A gamete from each parent fuses to form a zygote.

Genetic info from each gamete is mixed - zygote = unique.

Question 3

What are gametes?

Answer 3

Sex cells (sperm cells/egg cells)
Haploid (half no of chromosomes)

Question 4

What is meiosis?

Answer 4

Form of cell division involved in formation of gametes
Chromosome number is halved
Involves 2 divisions

Question 5

What must occur prior to meiosis?

Answer 5

Interphase

Question 6

Why is meiosis important for sexual reproduction?

Answer 6

Increases genetic variation

Ensures resultant zygote is diploid

Question 7

Advantages of sexual reproduction?

Answer 7

Creates genetic variation, increasing probability of species adapting to and surviving environmental changes

Question 8

Disadvantages of sexual reproduction

Answer 8

2 parents needed. Makes difficult in endangered populations or species which exhibit solitary lifestyles.
More time + energy required = fewer offspring produced.

Question 9

What is asexual reproduction?

Answer 9

Type of reproduction
Involves mitosis
Produces genetically incentivar offspring known as daughter cells

Question 10

Advantages of asexual reproduction ?

Answer 10

Only 1 parent needed
Lots of offspring produced in short time - enables rapid colonisation of area + reduce competition from other species
Requires less emergy

Question 11

Disadvantage of asexual reproduction?

Answer 11

No genetic variation (except spontaneous mutations) reducing probability of species being able to adapt to environmental changes.

Question 12

What type of reproduction is meiosis used for?

Answer 12

Sexual

Question 13

What is DNA

Answer 13

Double stranded polymer of nucleotides, wound to form a double helix

Question 14

What are the monomers of DNA?

Answer 14

Nucleotides

Question 15

What are DNA nucleotides made up of?

Answer 15

Common sugar
Phosphate group
One of 4 bases - A T C G

Question 16

State the full names of the 4 bases found in nucleotides

Answer 16

Adenine
Thymine
Cytosine
Guanine

Question 17

Describe how nucleotides interact to form a molecule of DNA

Answer 17

Sugar + phosphate molecules join to form sugar-phosphate backbone in each strand.
Base connected to each sugar.
Complementary base pairs joined by weak hydrogen bonds.

Question 18

Define genome

Answer 18

The entire genetic material of an organism

Question 19

What is a chromosome?

Answer 19

A long coiled molecule of DNA that carries genetic info in form of genes

Question 20

Define gene

Answer 20

A section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein

Question 21

Describe the method used to extract DNA from fruit

Answer 21

1. Place piece of fruit in beaker + crush
2. Add detergent + salt. Mix.
3. Filter mixture + collect liquid in test tube
4. Pour chilled ethanol into test tube
5. DNA precipitates forming a fibrous white solid
6. Use glass rod to collect DNA sample

Question 22

Why is detergent added to crushed fruit?

Answer 22

Disrupts cell membranes, releasing DNA into solution

Question 23

Why is salt added to the crushed fruit?

Answer 23

Encourages precipitation of DNA

Question 24

Why is chilled ethanol added rather than water?

Answer 24

DNA is insoluble in ethanol, encouraging its precipitation.

Question 25

What did Mendel study?

Answer 25

He studied inheritance of diff phenotypes of pea plants.

Question 26

What did Mendel establish a correlation between?

Answer 26

Parent and offspring phenotypes

Question 27

What did Mendel note about inheritance?

Answer 27

It was determined by ‘units’ passed on to descendants

Question 28

What is a mutation?

Answer 28

Random change in base sequence of DNA resulting in genetic variants

Question 29

What’s the effect of a gene mutation in coding DNA?

Answer 29

If mutation changes amino acid sequence, protein structure + function may change

Question 30

What is non-coding DNA

Answer 30

DNA which doesn’t code for protein but controls gene expression

Question 31

Why was Mendel work overlooked initially?

Answer 31

Scientists didn’t understand it as there was no knowledge of genes or DNA at the time

Question 32

What is a chromosome?

Answer 32

Long coiled molecule of DNA that carries genetic info in form of genes

Question 33

Define gene

Answer 33

A section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein

Question 34

What are alleles?

Answer 34

Different versions of the same gene

Question 35

Define genotype

Answer 35

An organisms genetic composition, describes all alleles

Question 36

Define phenotype

Answer 36

An organisms observable characteristics due to interactions of the genotype + environment

Question 37

Define homozygous

Answer 37

Having 2 identical alleles of a gene | Eg: FF or ff

Question 38

Define heterozygous

Answer 38

Having 2 different alleles of a gene | Eg: Ff

Question 39

What is a dominant allele?

Answer 39

Describes an allele that is always expressed | Represented with capital letter (F)

Question 40

What is a recessive allele?

Answer 40

Allele that is only expressed in the absence of a dominant allele Represented with small letter (f)

Question 41

What is a monohybrid inheritance?

Answer 41

Inheritance of a single gene

Question 42

What is the problem with single gene crosses?

Answer 42

Most characteristics are controlled by multiple alleles rather than just one

Question 43

What are sex chromosomes?

Answer 43

A pair of chromosomes that determine sex: Males = XY Females = XX

Question 44

Why does the inheritance of a Y chromosome mean that an embryo develops into a male?

Answer 44

Testes development in an embryo is stimulated by a gene present on the Y chromosome

Question 45

A couple have a child. What’s the probability that the child is female?

Answer 45

50% chance

Question 46

How can monohybrid inheritance be represented, other than a punnet square?

Answer 46

Family pedigree

Question 47

What is a sex-linked characteristic?

Answer 47

A characteristic that is coded for by an allele found on a sex chromosome

Question 48

What is co-dominance?

Answer 48

When 2 dominant alleles are expressed together in same individual

Question 49

When are multiple alleles present?

Answer 49

When 3 or more alleles are present at same loci

Question 50

An example of co-dominance/multiple alleles?

Answer 50

ABO blood group system

Question 51

Is the O allele recessive or dominant?

Answer 51

Recessive

Question 52

What are the A and B alleles?

Answer 52

Dominant