Genetics & Development ( + Textbook Chapter 4 )

Question 1

Why is neural anatomy described as ‘plastic’?

Answer 1

It undergoes rapid changes, particularly during early development, but continues to adapt throughout our lives.

Question 2

What is the definition of a gene?

Answer 2

A ‘fundamental unit of heredity’ that ‘maintains its structural identity from one generation to the next’.

Genes sometimes do not have ‘discrete loactions’, and may ‘overlap’ along chromosomal regions.

Moreover, some genes may alter the expression of others without coding for their own distinct protein.

Question 3

Describe:

The central dogma of biochemistry.

Answer 3

This describes the flow of genetic information, from DNA > RNA > Proteins during gene expression.

Note though that ‘information’ can flow backwards too via reverse transcription.

Moreover, information can go straight from RNA > Protein.

Question 4

Define:

Allele

Answer 4

Alternative forms of a gene located at the same loci on a chromosome.

These arise from mutations in the base sequence of that segment of DNA.

Question 5

Define:

Homozygous

(Genotype)

Answer 5

Possessing two identical copies of an allele for a particular gene.

Question 6

Define:

Heterozygous

(Genotype)

Answer 6

Possessing non-identical copies of alleles for a particular gene.

Question 7

Define:

Complete dominance in genetic expression.

Answer 7

When the dominant allele fully ‘masks’ the recessive allele and so its corresponding trait is expressed in both homozygous dominant (AA) and heterozygous (Aa) genotypes.

In order for the recessive allele to have its phenotype expressed, the genotype would need to be homozygous recessive (aa).

Question 8

List:

FOUR reasons why inheretence does not always follow the simplistic ‘single gene, single outcome’ model.

Answer 8

• Most of human characteristics are polygenic.
• Many traits are multifactoral (i.e. involve environmental effects).
• Some genes are pleiotropic (affect multiple characteristics).
• Epigenetic considerations.

Question 9

Define:

Pleiotropic genes.

Answer 9

Genes that affect multiple phenotypes.

These phenotypes are also ‘seemingly unrelated’.

Question 10

Compare & Contrast:

Sex-linked vs. autosomal genes.

Answer 10

• Sex-linked genes have loci on the sex chromosomes (X & Y in mammals).
• Autosomal genes are found on any other chromosome.

Question 11

How do sex-limited genes differ from sex-linked genes?

Answer 11

Sex-limited genes exist within the genome of both sexes of a species, but are active majority in one sex, and are activated by sex hormones.

Sex-limited genes occur on autosomal chromosomes, whilst sex-linked genes are found only on sex chromosomes.

Question 12

Define:

Epigenetics

Answer 12

Changes in gene expression that do not involve alterations to the base sequence of the DNA.

This contrasts mutations, which change genes and their expression through substituition, deletion or insertion of different nucleotides into the genomic sequence.

Question 13

True or False:

Forming new memories or habits can increase the activity of specific genes in certain neurons.

Answer 13

True

This is facilitated by epigenetic changes.

Question 14

True or False:

Epigenetic changes occur only in one generation and cannot be passed onto offspring.

Answer 14

False

it has been shown that epigenetic effects on genes and traits may be inherited at least through one or two generations.

Question 15

What is the typical structure/’format’ of the DNA within the cell at most stages of the cell cycle?

Answer 15

DNA is typically in its condensed chromosomal form, in which it is supercoiled and wrapped around histone proteins.