Chapter 7 and 8

Question 1

Summary of the influences on an organism’s phenotype

Answer 1

An organism’s phenotype is influenced by the interaction between their genes and their environment, as well as any epigenetic modifications that may selectively influence the expression of their genes.

Question 2

What does DNA methylation do?

Answer 2

Methylation usually serves to repress gene expression.
Methyl groups present on a DNA molecule tend to survive mitotic cell division.
Hydrocarbon molecules bind to particular nucleotides.

Question 3

What does DNA methylation not do?

Answer 3

Methylation changes the function of a gene by altering its sequence.

Question 4

Epigenetic changes are said to be somatically heritable. This means that they?

Answer 4

Are able to persist within an organism across most of its lifespan due to being passed on to replicated cells.

Question 5

Describes the relationship between the environment and epigenetic changes?

Answer 5

Epigenetics can be understood as the bridge between the environment and gene expression, where environmental influences like chemical exposure can lead to biochemical changes to an organism’s genome.

Question 6

Proportionate heritability

Answer 6

Proportionate heritability suggests that not all variation in the phenotypes of a population can be explained by genetic factors alone. Instead, environmental factors such as diet and nutrition are said to also influence phenotype.

Question 7

Methylation

Answer 7

Methylation refers to the process by which small hydrocarbon molecules called methyl groups are attached to certain nucleotides in a DNA sequence so as to reduce the transcription of the gene.

Question 8

Structure of DNA

Answer 8

DNA is a long complex molecule made up of nucleotides. DNA is a double helix structure made up of sugar, phosphate, backbone and a nitrogenous base.

Question 9

Possible base pairs of DNA

Answer 9

Adenine-Thymine and/or Cytosine-Guanine Must be equal parts.

Question 10

Allele

Answer 10

A particular form of a gene with a unique nucleotide sequence.

Question 11

Woman with polyploidy

Answer 11

3 in a section

Question 12

Turner syndrome

Answer 12

Female missing a second sex chromosome

Question 13

Match the diploid number to the corresponding genetic abnormality.
2n+1
2n+2
2n-1
3n

Answer 13

Trisomy
Tetrasomy
Monosomy
Polyploidy

Question 14

Order of meiosis

Answer 14

Prophase, Metaphase, Anaphase. Telophase
2
Prophase, Metaphase, Anaphase. Telophase

Question 15

What happens in Meiosis 1

Answer 15

A diploid cell is split into 2 diploid cells

Question 16

Prophase 1

Answer 16

chromatin condenses into chromosomes, Homologous chromosomes line up in the centre and exchange genetic material (Crossing over) nuclear membrane breaks down and the centrioles begin to move to opposite poles.

Question 17

Metaphase 1

Answer 17

Spindle fibres form and attach themselves to the chromosomes.

Question 18

Anaphase 1

Answer 18

Spindle fibres contract pulling the sister chromatids to opposite poles.

Question 19

Telophase 1

Answer 19

Contractile ring forms. nuclear membrane may reform. Contractile ring pinch the cell resulting in cytokinesis (Cell splitting)

Question 20

Meiosis 2

Answer 20

exactly the same as mitosis except it pull apart chromatids which are referred to as chromosomes resulting in haploid gametes.

Question 21

Codominance

Answer 21

Occurs when there’s two dominant alleles
AA
Both Alleles are dominant and the phenotype is mixed.
E.G Yellow + Blue flower = Yellow and Blue flower

Question 22

Incomplete Dominance

Answer 22

Occurs when there’s 2 dominant alleles
AA
Alleles ‘Blend together’
Yellow Flower + Blue flower = green

Question 23

Complete domincance

Answer 23

A dominant Gene (Capital) masks a recessive gene. Aa
A = Dominant
a = Recessive