Topic 3 - Genetics

Question 1

What is sexual reproduction?

Answer 1

Type of reproduction

Involves the production of gametes by meiosis

A gamete from each parent fuses to form a zygote

Genetic information from each gamete is mixed so the resulting zygote is unique

Question 2

What is meiosis?

Answer 2

Form of cell division involved in the formation of gametes

Chromosome number is halved

Involves two divisions

Question 3

What must occur prior to meiosis?

Answer 3

Interphase

Question 4

Why is meiosis important for sexual reproduction?

Answer 4

It increases genetic variation

It ensures that the resultant zygote is diploid

Question 5

What is the advantage of sexual reproduction?

Answer 5

It creates genetic variation, increasing the probability of a species adapting to and surviving environmental changes.

Question 6

Describe the disadvantages of sexual reproduction

Answer 6

Two parents are required. This makes the reproduction difficult in endangered populations or in species which exhibit solitary lifestyles.

More time and energy is required so fewer offsprings are produced

Question 7

What is produced in meiosis?

Answer 7

4 haploid gametes

Question 8

Asexual reproduction?

Answer 8

Involves mitosis

Genetically identical offspring known as daughter cells.

Question 9

Describe the advantages of asexual reproduction

Answer 9

Only one parents is required

Lots of offspring can be produced in a short period of time, enabling the rapid colonisation of an area and reducing competition from other species

Requires less energy

Question 10

What is the disadvantage of asexual reproduction?

Answer 10

No genetic variation (except from spontaneous mutations) reducing the probability of a species being able to adapt to environmental change

Question 11

What is DNA

Answer 11

A double-stranded polymer of nucleotides, wound to form a double helix.

Question 12

What are monomers of DNA?

Answer 12

Nucleotides

Question 13

What are DNA nucleotides made up of?

Answer 13

Common sugar
Phosphate group
One of four bases: A,T,C or G

Question 14

Describe how nucleotides interact to form a molecules of DNA

Answer 14

Sugar and phosphate molecules join to form a phosphate-sugar backbone in each DNA strand

Base connected to each sugar

Complementary base (A pairs T, C pairs with G)

Question 15

Define genome

Answer 15

The entire genetic sequencing of an organism

Question 16

Define gene

Answer 16

A section of a DNA molecule that codes for a specific protein.

Question 17

What is a chromosome?

Answer 17

A long, coiled molecules of DNA that carries genetic information in the form of genes.

Question 18

Describe the method to used to extract DNA from fruit

Answer 18

Question 19

Why is detergent added to crushed fruit?

Answer 19

It disrupts the cell membranes, releasing DNA into solution

Question 20

Why is salt added to the crushed fruit?

Answer 20

Salt encourages the DNA to clump together

Question 21

Why is chilled ethanol added rather water

Answer 21

DNA is insoluble is ethanol, encourage its precipitation

Question 22

Outline how the work of Mendel helped scientists to develop their understanding of genetics?

Answer 22

Mendel studied the inheritance of different
phenotypes of pea plants

He establishes a correlation between parent and offsprings phenotypes

He noted that inheritance was determined by “units” passed onto descendants

Using gene crosses, he devised the terms “dominant” and “recessive”

Question 23

Why was Mendel’s work initially overlooked

Answer 23

Scientist’s didn’t understand Mendel work as there was no knowledge of genes or DNA at that time.

Question 24

What is a chromosome?

Answer 24

A long, coiled molecule of DNA that carries genetic information in the form of genes

Question 25

What are alleles?

Answer 25

Different versions of the same gene

Question 26

Define genotype

Answer 26

An organism’s genetic composition describes all alleles

Question 27

Define phenotype

Answer 27

An organism observable characteristics due to interactions of the genotype and environment (which can modify the phenotype)

Question 28

Define homozygous

Answer 28

Having two identical alleles of a gene

FF or ff

Question 29

Define heterozygous

Answer 29

Having two different alleles of a gene e,g Ff

Question 30

What is a dominant allele?

Answer 30

Describes an allele that is always expressed

Representes with a capital letter e,g F

Question 31

What is a recessive allele?

Answer 31

An allele that is only expressed in absence of a dominant alleles
Represented with a small letter e,g f

Question 32

What is monohybrid inheritance?

Answer 32

The inheritance of a single gene

Question 33

Answer 33

Question 34

Answer 34

Question 35

What are sex chromosome?

Answer 35

A pair of chromosomes that determine sex :
Males have an X and a Y chromosome
Females have two X chromosomes

Question 36

Answer 36

Question 37

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

Answer 37

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