Genetic Info

Question 1

Difference in dna and rna

Answer 1

DNA: double stranded, high molecular weight, deoxyribonucleic acid

RNA: single stranded, heterogenous in size, ribonucleic acid, uracil

Question 2

Difference between ribonucleic and deoxyribonucleic

Answer 2

Ribo has hydroxyl group 2nd carbon

Question 3

Why is RNA unstable?

Answer 3

Has extra hydroxyl group on 2nd carbon so can be attacked by water

Adv as cels change expression pattern

Question 4

What is a purine?

Answer 4

A and G

Question 5

What is T and C

Answer 5

Pyrimidines

Question 6

Why can several mRNAs be transcribed from some genes

Answer 6

Because exons spliced differently

Question 7

How many chromosomes

Answer 7

22 autonomies and 1 sex chromosome

Question 8

How is dna packaged

Answer 8

Packaged into chromatin by histones and other chromosomal proteins

Question 9

How can chromosomes be identified

Answer 9

By banding pattern

Question 10

What is upstream and downstream

Answer 10

5’ upstream
3’ downstream
Read in 5’ to 3’ direction

Question 11

Repeated sequences in dna

Answer 11

50%
Often occur in blocks of tandem repeats
Called satellite DNA

Question 12

Types of satellite DNA

Answer 12

Minisatellite - highly polymorphic 1000 copies in one block. Found at telomeres.

Microsatellite - smaller. Usually intergenic/ Intronic

Question 13

Importance of minisatellites at telomeres

Answer 13

-Repeats create heterochromatin at tips which helps protect chromosomes from being digested by nucleuses

-Allows replication of DNA to the tips

Question 14

Repeats can have negative effects. How?

Answer 14

They can cause mispairing during cell division to give:
• Large scale duplication/deletion between homologous chromosomes
• Translocation of DNA between non-homologous chromosomes

Question 15

Germline cells?

Answer 15

Cell that divide to generate the gametes

Oocytes (eggs females born with) and spermatogonium

Question 16

RNA that isnt translated into proteins?

Answer 16

tRNA and rRNA involved in translation of mRNA

But some RNA molecules modify other RNA molecules (snRNA; snoRNA)
microRNA (miRNA)- Bind to 3’UTR of mRNA and inhibit translation

Question 17

What does detergent treatment of nucleus cause

Answer 17

causes release of decondensed chromatin threads from non-dividing
(interphase cells)

Question 18

What is the fundamental unit of chromatin?

Answer 18

Nucleosome - DNA wound around a histone core

Question 19

How are Decondensed chromosomes still structurally organised in non- dividing cells

Answer 19

• Attachment to nuclear skeleton
• has a functional role, for example the clustering of ribosomal
  genes in the nucleolus

Question 20

Heterochromatin

Answer 20

Found at centromeres and telomeres

Highly condensed region of an interphase chromosome

Generally gene poor and transcriptionally inactive

Question 21

Euchromatin

Answer 21

Prevalent in gene rich areas
less compact allowing access for proteins involved in transcription

Question 22

Nucleolus

Answer 22

Large structure in the nucleus

Where ribosomal RNA is transcribed and ribosomal subunits are assembled

Question 23

Two types of chromatin in chromosomes

Answer 23

1. Euchromatin
2. Heterochromatin

Question 24

How many histone molecules in a nucleosome made of

Answer 24

8

Question 25

DNA packaging

Answer 25

1. DNA wraps around histones 2. Nucleosomes fold up into chromatin 3. Fibres compressed further 4. Fibres coil up to produce chromatid of a chromosome

Question 26

Why can protein synthesis not occur during mitosis

Answer 26

because the DNA is so condensed so enzymes e.g. RNA polymerase can’t access it.

Question 27

Kinetochores

Answer 27

spindle microtubules attach to the two kinetochores (one for each sister chromatid) at the centromere

Question 28

Two types of heterochromatin

Answer 28

1. Facultative heterochromatin In temporarily inactivated (condensed) state 2. Constitutive heterochromatin Always inactive and condensed. Preset at centromere and telomeres.

Question 29

What are dNTPs

Answer 29

Required for replication and repair of dna They are the building blocks of DNA they lose two of the phosphate groups when incorporated into DNA during replication via phosphodiester Bond

Question 30

What are replication origins

Answer 30

Sites where replication can start Have certain sequences that are recognised Start codon AUG

Question 31

Which end can DNA polymerase add nucleotides

Answer 31

3’

Question 32

What must DNA polymerase require

Answer 32

dNTPs Template RNA primer

Question 33

Okazaki fragment

Answer 33

Synthesised in opposite direction to movement of fork in small fragments Fragments joined together by DNA ligase

Question 34

Leading strand

Answer 34

Synthesised in same direction of fork continuous synthesis

Question 35

Lagging strand

Answer 35

Lagging strand synthesised discontinuously In opposite direction to movement of fork Requires new RNA primers DNA polymerase adds to new RNA primers to start a new Okazaki fragment RNA primers removed and replaced with DNA using DNA ligase

Question 36

What synthesises RNA primers

Answer 36

DNA primase

Question 37

Role of DNA polymerase

Answer 37

Add nucleotides on 3’ of new strand Proof read

Question 38

Replication bubbles ?

Answer 38

Form at multiple origins along length of chromosome Spread out in both directions until all unite Efficient and fast replication

Question 39

Chemical reactions which manage dna

Answer 39

Dpurination - base is lost Deamination - C to U UV - adjacent thymines become a dimer

Question 40

What does Nucleosome consist of

Answer 40

Composed of 8 histones of 4 types Roughly 140bp of DNA

Question 41

DNA positively charged.

Answer 41

No. Negatively charge. Sugar phosphate backbone is negatively charged

Question 42

Amino acids positively charged?

Answer 42

Yes

Question 43

Enzymes that involved in acetylation

Answer 43

Histone acetyl transferases add acetyl Histone deacetylase remove acetyl

Question 44

What can be used to track a gene

Answer 44

Microsatellites in non coding regions

Question 45

Function of micro RNA

Answer 45

To repress synthesis of a protein

Question 46

Genomic imprinting

Answer 46

Epigenetic change the process by which only one copy of a gene in an individual (either from their mother or their father) is expressed, while the other copy is suppressed