Centra Dogma + Genetic Variation

Question 1

describe 3 parts of nucleotides

Answer 1

1. deoxyribose (5 carbon sugar) OH on 3’ carbon
2. phosphate group
3. nitrogenous base on 1’ (ATGC)

Question 2

name three binding/links to form DNA

Answer 2

1. sugar phosphate backbone
2. hydrogen bonding (bt bases)
3. phosphodiester linkage (link bt OH and phosphate)

Question 3

number of hydrogen bonds between A–T and G–C

Answer 3

2 h bonds bt A–T and 3 bt G–C

Question 4

measuring of single stranded DNA can be in .. and measuring of double stranded DNA can be in ..

Answer 4

nucleotides

base pairs

Question 5

Name the 5 nitrogenous base pairs

Answer 5

Adenine
Thymine
Guanine
Cytosine
Uracil (replaces T in RNA)

Question 6

what direction are DNA strands written in? and what direction is DNA twisted in? How many base pairs per turn?

Answer 6

Right, Right
“right handed DNA” (picture right hand walking up staircase)
10 base pairs per turn

Question 7

What is on the end of the 5’ of DNA strand versus the 3’ end?

Answer 7

5’ end has free phosphate group

3’ end has free OH’ on 3 carbon

Question 8

describe how DNA is packaged in nucelus

Answer 8

DNA helix is wound around histone proteins forming nucleosomes
* 150 base pairs wound around each histone
packaged as chromatin
nucleus has 2 copies of DNA one from each parent (46 total - 23 from each parent)

Question 9

describe the Central dogma

Answer 9

DNA-> RNA-> Protein

transcription - translation

Question 10

difference bt DNA & RNA

Answer 10

DNA: double stranded, uses T, OH on 3’ sugar
RNA: single stranded, uses U, OH on 3’ and 2
carbon on sugar
* • RNA offers portability, DNA stays in nucleus, RNA can move to cytoplasm and be translated to proteins

Question 11

describe the 3 regulatory regions of DNA to express a gene

Answer 11

1. promoter region- upstream but directly next to the gene
2. enhancers- small regulatory regions more upstream than promoter
   enhancers and promoter regions have binding sites for transcription factors
3. terminator region - downstream

Question 12

enzyme that mediates transcription, it is recruited to promoter region to Transcription start site (TSS) to begin transcribing from 5-> 3 producing single strand RNA molecule

Answer 12

RNA Polymerase II (RNAPII)

Question 13

describe splicing and processing after transcription of DNA - RNA

Answer 13

RNA splicing : exons stay, introns are spliced out

RNA processing : cap is added to 5’ end and tail is added to 3’ end (protection)

Question 14

start codon and stop codons

Answer 14

AUG

UGA, UAA, UAG

Question 15

what region of mRNA from translation can affect translation initiation, can affect RNA stability, and is transcribed but (not translated)

Answer 15

5’UTR

Question 16

common variant affecting one nucleotide, it is common in population
* contributes to why we see difference in phenotypes between people from a change in genotype

Answer 16

SNP (single nucleotide polymorphism)

Question 17

Changes in genotype that affect phenotype arise from changes in RNA/protein levels or protein function. Name some changes.

Answer 17

changes in
1.) RNA/protein levels
◦ enhancer/promoter region changes that reduce amount of RNA produced can lead to decrease in protein levels
◦ changes in 5’ or 3’ UTR can lead to decrease in stability of RNA molecule and decreased RNA & protein levels
◦ changes in 5’ UTR can also cause decrease in translation initiation - lead directluy to decrease in protein levels

2.) Protein function
◦ location of protein coding region
◦ ex: SNP in protein coding region, will it disrupt protein function?
◦ it depends on the coding
◦ silent variant - has no change
◦ missense variant - variation that converts one amino acid to another
◦ nonsense variant - codes for stop codon
◦ frame shift variant - inserts base and shifts all downstream codons usually ends earlier in stop codon
◦ all can really change protein outcome depending on type/location of change

Question 18

Lactose intolerance

Answer 18

deficency in lactase enzyme - responsible for cleaving lactose
infants/children - express the enzyme critical for nutrition breast milk
lactase levels in small intestine decrease with age
allowing some lactose to pass uncleaved into small intestine
here it is fermented by gut microbes - producing gases & distress
treated- UTC supplements contain lactase enzyme - temporarily increases enzyme levels in gut
SNP is associated with adult onset lactose intolerance- located upstream of LCT gene which encodes lactase enzyme

the SNP is in enhancer region - in OCT-1 binding site which could be C or T
• T version creates higher affinity for oct-1 which leads to greater expression of LCT
• T version means ur good for lactose into adulthood
• Amy has C version which has lower affinity binding of oct-1 cant express LCT