Human Genetics 3

Question 1

steps of dna replication

Answer 1

1. helicase unwinds
2. single strand binding proteins keep unwound
3. primase adds short RNA primer
4. leading strand synthesised by polymerase III 5’ >3’ (reading off 3-5)

Question 2

explain lagging /leading strand

Answer 2

1. Extension of the strand can only happen in 5’-3’ direction

• Only one strand can get extended continuously= leading strand

1. Other strand created discontinuously = lagging strand
2. Gets replicated by addition of short Okazaki fragments

Question 3

explain polymerase 1 and ligase do

Answer 3

lagging strand
- 1. Enzyme DNA polymerase I replaces RNA primers with DNA
• Enzyme DNA ligase closes the polypeptide stands

Question 4

What are DNA polymerases proof reading roles

Answer 4

3. Excision of incorrectly incorporated nucleotides by 3’ > 5’ exonuclease activity
4. mistake gets corrected before more of the strand with the error is created

Question 5

what are the 3 levels of mutation

Answer 5

gene
chromsome
genome

Question 6

3 types of gene mutation

Answer 6

1. Base subs
2. Base insertion or deletion
3. Copy number variation

Question 7

3 types of chromosomes mutation

Answer 7

1. Inversion
2. Translocation
3. Deletion

Question 8

type of genome level mutation

Answer 8

1. Change in number of chromosomes

Question 9

what the universal start codon bases

Answer 9

AUG

Question 10

What are base subsitutions

Answer 10

point mutations= single nucleotide polymorphisms

• Replacement of one nucleotide in DNA by another (T -> C)

Question 11

three types of base substitutions

Answer 11

synonymous(silent)= same AA
missense (changed AA)
Nonsesnse = STOP codon

Question 12

what are base insertions/deletions also known as

Answer 12

frameshift mutation

Question 13

what can copy number variation gene mutation effects in cell

Answer 13

amount of protein made

Question 14

what translocation

Answer 14

• Fragment of a chromosome is moved from one chromosome to another

Question 15

what are two options of division of stem cells

Answer 15

self renewal

differentiaition

Question 16

what are the two signals that cause differentiation of stem cells > diff tissues

Answer 16

1. Internal signals: changes in transcription or expression of genes expression regulates cell differentiation
2. External signals: chemicals secreted by other cells, physical contact with neighbouring cells, molecules in the microenvironment of the cell

Question 17

prevalence vs incidence

Answer 17

Prevalence: number of people alive with a prior diagnosis of cancer at a given time
Incidence: number of new cancers diagnosed within a given period of time

Question 18

3 causes of cancer

Answer 18

genetics
oncoviruses
environment

Question 19

two types of reproduction

Answer 19

asexual and sexual

Question 20

advantages of asexual reproduction

Answer 20

Speed, no gamete formation necessary – very quick
Advantage for small populations e.g. in secluded areas
Not very complex, requires less energy compared to sexual reproduction
Advantage in stable environment

Question 21

disadvantages for asexual reproduction

Answer 21

Offspring is clone of parent -> little genetic diversity
Environment usually not stable long term -> want to have
diversity to be able to adapt to different environments
Often struggle for existence as well as overcrowding

Question 22

advantages of sexual reproduction

Answer 22

Introducing genetic diversity
-> allows for adaptation to a changing
environment

Question 23

disadvantages of sexual reproduction

Answer 23

Cost intensive – a lot of energy
Only 50% of the genome contribute to
the offspring
Fewer offspring

Question 24

Prep for meisosis= what does DNA replication do

Answer 24

2n (one maternal one paternal)

> two maternal two paternal (connected at centromere)

Question 25

what two processes results in variation in sexual reproduction

Answer 25

crossing over

independent assortment

Question 26

what are the division names of meiosis 1 and 2 and main divisional occurrences

Answer 26

Meiosis I: Reductional Division (homologous chromosomes seperate)
Meiosis II: Equational Division (sister chromatids seperate)

Question 27

explain stages of meiosis I

Answer 27

P1: condense + form chromosomes, crossing over occurs
M1: align at equator
A1: homologous chrome opposite poles by spindles
T1: reform nucleus

Question 28

at the end of Meiosis 1, are they haploid or diploid

Answer 28

haploid= but have chromo still duplicated

Question 29

what is interkinesis

Answer 29

period b/w 1st 2nd meiosis

Question 30

stages of meiosis II

Answer 30

same as Meiosis I but at anaphase sister chromosomes split

Question 31

at the end of Meiosis II, are they haploid or diploid

Answer 31

4 haploid cells (n, 23)