1. Basic principles of genetics

Question 1

What is the difference between heredity and variation?

Answer 1

HEREDITY: offspring are similar to their parents

VARIATION: offspring are different from their parents (and each other)

Question 2

What is the difference between genotype and phenotype?

Answer 2

Genotype genes that influence phenotype

Phenotype is what is expressed

Question 3

What is the difference between eukaryotes and prokaryotes? (3)

Answer 3

Eukaryotes: Multicellular, has membrane bound nucleus, nuclear genes on multiple linear chromosomes
(Animals, plants, fungi and protists)

Prokaryotes: unicellular, NO nucleus, single circular chromosome
(Bacteria)

Question 4

What are chromosomes made up of?

and what is this made up of?

Answer 4

Chromatin

Made up of DNA and histones (DNA wrapped around histones)

Question 5

What is euchromatin?

Answer 5

loosely packed chromatin that can be readily transcribed

Question 6

What is heterochromatin?

Answer 6

Condensed structure that does not allow expression of genes in that region

Question 7

What are modifications to chromatin structure controlled by?

Answer 7

Controlled by addition of methyl and acetyl groups to the histone proteins
(characteristics are heritable)

Question 8

How can gene activity be altered without changing the DNA sequence?

Answer 8

Modifications to chromatin structure

Question 9

Describe the structure of linear chromosomes? (4)

Answer 9

Telomeres: structures at each end of linear chromosomes that protect them from degradation

Centromere: “specialised region that acts as a site for the binding of kinetochore proteins”

p arm (stands for “petite”) = shorter chromosome arm
q arm (it’s the letter after p) = longer chromosome arm

Question 10

What are the positions of protein coding regions known as?

Answer 10

Loci (Locus singular)

Question 11

What is Cytogenetics?

Answer 11

The study of chromosomes

Question 12

What is a technique used to study chromosomes?

What chemical is used to stain chromosomes and give unique banding pattern?

Answer 12

G-banding

Giemsa

Question 13

What is a Karyotype

Answer 13

The chromosome complement of an individual

Question 14

How many autosomes in a typical human Autosome?

Answer 14

1-22

Question 15

What are the chromosome combinations for male and female?

Answer 15

XX = Female
XY = Male

Question 16

How many copies of each chromosome does a nucleus have?

Answer 16

2 (diploid)

Question 17

What is mutation?

Answer 17

The process that produces a gene or a chromosome set differing from that of the wild type/The gene or chromosome set that results from such a process

Question 18

What does wild type mean?

Answer 18

The form that predominates in nature / in a standard laboratory stock

Question 19

What does Polyploidy mean?

Answer 19

Unusual number of chromosome sets

Question 20

what does aneuploidy mean?

Answer 20

One or a few individual chromosomes extra / missing

Question 21

What is:
Trisomy
Monosomy

Answer 21

Trisomy = 3 homologues instead of 2
Monosomy = 1 homologue instead of 2

Question 22

What do these large-scale chromosomal rearrangements mean:
Deletions:
Inversions:
Translocations:

Answer 22

Deletions: part of the chromosome is missing
Inversions: part of the chromosome has been flipped
Translocations: part of the chromosome has been moved

Question 23

What are sources of mutation?

Answer 23

Mistakes during replication:

• Point mutations
• Small insertions / deletions -> frameshifts

Genes interrupted by transposons

DNA breaks incorrectly repaired

Question 24

What do these types of point mutations mean?

Silent:
Nonsense:
Missense:

Answer 24

Silent: no change to amino acid sequence

Nonsense: introduction of a stop codon into the gene

Missense: changes the amino acid sequence (this will have varying effects on protein function. “Null allele” = total loss of function)

Question 25

What is an allele?

Answer 25

Different versions of a gene

Question 26

What is an example of a genetic disease caused by rare, recessive, autosomal alleles?

Answer 26

Example: phenylketonuria Caused by mutations in the gene for phenylalanine hydroxylase, involved in the metabolism of phenylalanine amino acid Lack of functional enzyme causes harmful build-up if Phe in the body -> intellectual disability, seizures But one functional copy is sufficient for metabolism - PP homozygous dominant: normal Phe metabolism - Pp heterozygous: normal Phe metabolism - pp homozygous recessive: PKU

Question 27

Where is most eukaryotic genetic material found?

Answer 27

Nuclear chromosomes | also some in mitochondria and chloroplasts