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Flashcards in The genome Deck (23):
1

Somatic cell

23 pairs of chromosomes in the nucleus
22 autosomal pairs and 1 pair of sex chromosomes

2

Chromosome

2 chromatids joined at the centromere
Single molecule of DNA

3

Chromatid

1 copy of the duplicated chromosome

4

Chromatin

Double stranded DNA macromolecule wrapped around histone proteins

5

DNA

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

6

Genome

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

7

Cell cycle

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

8

Mitosis

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

9

Meiosis

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

10

Non-disjunction

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

11

Aneuploidy

Abnormal chromosome numbers

12

Genetic coding

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

13

Gene anatomy

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

14

Reading frames

mRNA is read in groups of three (triplet) = codons
Each codon specifies a particular amino acid along peptide

15

Redundancy

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

16

Variants

Alterations to DNA sequences
Responsible for evolutionary change

17

Mutations

Disease-causing variants

18

Single gene mutations

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

19

Haploinsufficiency

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

20

Silent mutation

Do not affect the amino acid produced by a codon

21

Missense mutation

Affect the amino acid produced by a codon

22

Nonsense mutation

Result in a stop odon

23

Frameshift mutation

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