The genome

Question 1

Somatic cell

Answer 1

23 pairs of chromosomes in the nucleus

22 autosomal pairs and 1 pair of sex chromosomes

Question 2

Chromosome

Answer 2

2 chromatids joined at the centromere

Single molecule of DNA

Question 3

Chromatid

Answer 3

1 copy of the duplicated chromosome

Question 4

Chromatin

Answer 4

Double stranded DNA macromolecule wrapped around histone proteins

Question 5

DNA

Answer 5

Single double stranded macromolecule
4 base pairs (A, C, T, G); A-T and C-G by complementary base pairing with H-bond
Deoxyribose (alternating phosphate and sugar) backbone

Question 6

Genome

Answer 6

Total complement of info from all chromosome
25 000 genes
1-2 % of genome codes for proteins (exome)

Question 7

Cell cycle

Answer 7

M - Mitosis
G1 - Gap 1 —> G0 (non-dividing cells)
S - Synthesis
G2 - Gap 2

Question 8

Mitosis

Answer 8

1 mother –> 2 genetically identical daughter cells
Parent cell
Chromosome duplication
Prophase
Metaphase (chromosome align at metaphase plate)
Anaphase (sister chromatids separate during anaphase)
Telophase
SOMATIC CELLS

Question 9

Meiosis

Answer 9

1 parent –> genetically different daughter cells
Parent cells
Chromosome duplication
Prophase I (tetrad form by synapsis of homologous chromosomes)
Metaphase I (tetrads align at metaphase plate)
Anaphase I (homologous chromosome separate)
Sister chromatids remain together
Telophase I
Meiosis II
Anaphase II (no further duplication, sister chromatids separate)
GONAD CELLS

Question 10

Non-disjunction

Answer 10

Failure of homologous chromosomes or sister chromatids to separate properly during cell division

Question 11

Aneuploidy

Answer 11

Abnormal chromosome numbers

Question 12

Genetic coding

Answer 12

Code for peptide (protein) via intermediate messenger RNA (mRNA)
Code directly for ribosomal RNA (rRNA)
Code direct for transfer RNA (tRNA)

Question 13

Gene anatomy

Answer 13

Exons - code for protein (express)
Introns - found between eons (intervening)
Regulatory sequence control when/where/how much gene expressed; include
- promoter region (5’ end, upstream of first exon)
- enhancer/silencer regions

Question 14

Reading frames

Answer 14

mRNA is read in groups of three (triplet) = codons

Each codon specifies a particular amino acid along peptide

Question 15

Redundancy

Answer 15

Largely occurs in the third position
64 codon combinations but only
20 amino acids

Question 16

Variants

Answer 16

Alterations to DNA sequences

Responsible for evolutionary change

Question 17

Mutations

Answer 17

Disease-causing variants

Question 18

Single gene mutations

Answer 18

Affect a single base (point mutation), a small number of bases or large sequence of bases
3 classes
- base substitutions (silent/synonymous mutation, nonsense mutation, missense mutation)
- deletions
- insertions

Question 19

Haploinsufficiency

Answer 19

Reduction by about half in amount of protein, usually due to whole gene deletion

Question 20

Silent mutation

Answer 20

Do not affect the amino acid produced by a codon

Question 21

Missense mutation

Answer 21

Affect the amino acid produced by a codon

Question 22

Nonsense mutation

Answer 22

Result in a stop odon

Question 23

Frameshift mutation

Answer 23

Alters the reading frame, may lead to an entirely different protein or stop codon