3bio9

Question 1

What does the central dogma describe
Wuz the ploidy number

Answer 1

The flow of genetic information (DNA, RNA and protein) in an organism
The number of copies of each chromosome

Question 2

Coding and noncoding DNA

Answer 2

Coding DNA is genes and it codes for a polypeptide. Noncoding DNA regulates gene expression and it is RNA molecule

Question 3

two models for dna replication
-models
-who found the right one

Answer 3

Conservative, where the original molecule stays fully intact and the copy is brand new. Semi conservative where the original molecule stays half intact and the copy is half new, where each strand is used as a template meselson and stahl said it was semi conservative

Question 4

Phases of
DNA replication

Answer 4

Initiation, elongation, termination and repair

Question 5

Dna replication initiation
-origin
- helicase
-SSBPs
-replication bubble and fork

Answer 5

The origin of replication is a DNA sequence that binds initiation enzymes. Starting there, DNA helicase unwinds and unzips the helix by slicing the hydrogen bonds, and sing’e stranded binding proteins keep the strands apart. The separated strands form the replication bubble, and the sides of the replication bubble are the replication fork,

Question 6

elongation phase of replication
-template
-RNA primase
-DNA polymerases
-leading and lagging strand
-DNA ligase

Answer 6

Each strand is used as a template. DNA adds new nucleotides but it needs a primer. RNA primase adds some RNA molecules and DNA polymerase three can then add a string of nucleotides called dNTP, to the three prime end. The strand built toward the replication fork is the leading strand and the strand built away from the replication fork is the lagging strand. The lagging strand requires multiple priners., and for it DNA polymerase builds between them in Okazaki fragments. DNA polymerase one replaces the rna primers, but it can’t connect the backbones of those nucleotides to the okazaki fragments. That is done by DNA ligase.

Question 7

Replication repair phase
-how often mistakes
-proofreaders

Answer 7

An average of one mistake happens per million base pairs, so DNA polymerase one and three can proofread their own work. When replication is done DNA polymerase two corrects the remaining errors.

Question 8

Wuz transcription
Phases of transcription

Answer 8

Creation of mRNA from a gene of DNA
Initiation, elongation, termination and processing

Question 9

promoter
-RNA polymerase
-sequence
-location

Answer 9

Transcription factors bind to a promoter and RNA polymerase binds to the factors. In eukaryotes the promoters sequence is TATAAA and it is on the nontemplate strand. It is upstream of the starting point and is not transcribed.

Question 10

Strands
-Promoter
-Other names
-template

Answer 10

In DNA replication The non template strand holds the promoter. It is the sense strand since it is the same sequence as the mRNA transcript. the template strand is the antisense or noncoding strand. In translation the mRNA is the template.

Question 11

Elongation phase of transcription
-in what direction
-promoter

Answer 11

RNA polymerase reads the template strand from three prime to five prime and synthesizes mRNA in the opposite direction. Transcription begins after the promoter.

Question 12

Changes made to pre mRNA

Answer 12

Five prime cap, polyadenation and rna splicing

Question 13

Telomeres
-Purpose
-Coding?
-sequence

Answer 13

DNA polymerase can only add to the three prime end, so the five prime end of the lagging strand cannot be extended and telomeres shorten with age. As a solution telomeres are noncoding and reapeating segments of 5-TAAGGG-3

Question 14

Why do codons have to be redundant

Answer 14

There are 64 codons and twenty amino acids

Question 15

Termination phase of transcription

Answer 15

When RNA polymerase reaches the termination sequence it transcrives the sequence and falls off the DNA. the mRNA also falls off. Its called pre mRNA. The sequence of the termination signal is 5’-TAAGGG-3’

Question 16

Processing phase of transcription (minus RNA splicing)
-Methyl guanosine
-polyadenation

Answer 16

Post transcriptional modifications are changes to pre mRNA to prepare it to leave the nucleus and protect it from degradation. a nucleotide called methyl guanosine can be added to the five prime end. polyadenation is the addition of a poly a tail to the three prime end. The rerminator sequence is also a polyadenation sequence.

Question 17

Rna splicing
-introns and exons

Answer 17

Excised from premRNA are the Noncoding regions in genes which are called introns. Spliced together are the coding regions of a gene which are called exons. They are translated into polypeptides. Different combinations of exons make different polypeptides.

Question 18

Genes
-define
-expressed

Answer 18

Genes are continuous strings of nucleotides that contain a region that codes for a RNA molecule. They start with a promoter and end with aterminator. When a polypeptide of a gene is made that gene is expressed.
Regulation of gene expression means to turn protein synthesis on or off.

Question 19

Translation
-define
-Phases

Answer 19

It is the creation of a polypeptide from an mRNA. The phases are Initiation, élongation and termination

Question 20

Ribosome
-identity
-structure
-function

Answer 20

A ribosome is an enzyme with a quaternary structure. It has a large and small subunit. The ribosome reads the mRNA and adds the corresponding amino acid for each codon.

Question 21

tRNA
-function
-structure
-number of different tRNAs
-initiatior tRNA

Answer 21

It delivers the right amino acid for a codon. It has a region that carries the amino acid called the amino acid attachment site and a region that carries an anticodon There are 64 different tRNAs.. the initiatior tRNA, which carries methionine, is binded to by the small ribosomal subunit.

Question 22

Initiation phase of translation
-initiatior
-binding sites

Answer 22

An initiator tRNA binds to the start codon, and it has a methionine. The ribosome has three sites. The A site binds the next tRNA, the P site holds the tRNA that is being added to the chain, and the E site releases tRNAs. The large ribosomal subunit binds to the small suchthat the initiatior tRNA is in the P site, leaving the A site to bind to the next tRNA.

Question 23

Elongation phase of translation
-bond
-order

Answer 23

A peptide bond is made between the amino acids that are in the P and A sites. Amino acids are added to the C terminus, so the polypeptide is made from the N to the C terminus. mRNA is read from five prime to three prime.

Question 24

Termination phase of translation
-stop codon
-release factor
-disassociate

Answer 24

The ribosome eventually reaches a stop codon, for which no tRNA exists. Instead a release factor binds. Thus The stop codon is excluded from the polypeptide. The ribosome disassociates from the mRNA.

Question 25

Mutation and polymorphism
-types of mutations
-possible effects on polypeptide
-Possible effects on DNA
- vs polymorphism

Answer 25

A mutation can be positive or negative or neither. Point mutations are small scale and involve a single base pair. Chromosome mutations involve more DNA. A frameshift mutation changes the reading frame. When they change the polypeptide, they phenotype changes. Mutations can be silent, having no effect on the polypeptide. They can be missense, changing any number of bases. Or they could be nonsense, causing a premature stop that results in a truncated protein. Amplification is when a portion pf DNA is copied reapeatedly. Theres also deletion, inversion and translocation. A mutation is a variation that exists in less than two percent of the population, when it becomes any more common it is a polymorphism. They can happen naturally as an uncorrected mistake of replication or they could be induced by environmental factors like radiation

Question 26

Gene expression in prokaryotes
-operons and components
-lac
-trp

Answer 26

Prokaryotes often have promoters that control clusters of genes called operons. Operons are transcribed into a single mRNA. The components are structural genes, operator and promoter. The genes in the operon are structural genes. The operator is the binding sequence for the activator or repressor. The lac operon regulates the expression of genes involved in the digestion of lactose. Expression is turned on when there is Lactose in the cell. The trp operon regulates the expression of genes involved in ehe synthesis of tryptophan. Expression is turned on by a shortage of tryptophan.

Question 27

Stages of eurkaryote gene expression

Answer 27

Transcriptional, post transcriptional, translational and post translational.

Question 28

Transcriptional regulation
-histones
-transcription factors

Answer 28

Transcriptional regulations are being Mechanisms that control transcription. DNA tight around histones is inaccessible and must unravel for transcription. Since RNA polymerase cant directly bind to a promoter gene expression can be controlled by controlling the production of transcription factors.

Question 29

Post transcriptional regulation

Answer 29

The mRNA is more likely to be degraded without the poly a tail and five prime cap. Alternative splicing can also occur.

Question 30

What is translational regulation

Answer 30

Controlling whether the ribosome small subunit binds

Question 31

Why can you control genes Post translation

Answer 31

many proteins must be modified before they become functional

Question 32

Meselson and stahl
-tested whom
-nitrogen source
-centrifuge

Answer 32

Meselson and stahl tested Francis and Cricks support for the semi conservative model. They grew ecoli for fourteen generations in N15 nitrogen with ammonium chloride as the nitrogen source. This ensures all the dna would be labelled with the nitrogen. They took a sample and added cesium chloride for centrifugation, then transferred some of the Bacteria into N14 medium. After the transfer they took a sample every 20 minutes, which is a generation. The samples were put in a centrifuge, which spun Fast enough to cause a higher Density solution to exist at the bottom of the tube. The dna moved to positions that matches their density. All dna was in the heavy for generation zero, but in an intermediate density in generation one. After two generations, half was light and half was intermediate.