Cellular Contril

Question 1

What does ligase do?

Answer 1

Joins small sections of DNA together during replication by joining deoxyribose molecules to phosphate molecules

Question 2

What does proof-reading endonuclease do?

Answer 2

Cuts of any wrongly paired bases during DNA replication

Question 3

What do all cells carry?

Answer 3

The same genes (DNA), but the structure and function of different cells vary. This is because not all genes are expressed

Question 4

What happens because of controlled gene expression?

Answer 4

Different proteins are made which modify the cell, including structure and processes that occur

Question 5

How does transcritpional level control occur?

Answer 5

By altering the rate of transcription of genes. This is controlled by transcription factors

Question 6

Explain transcription factors

Answer 6

This is a way of transcriptional level control. Transcription factors are proteins that bind to DNA and switch genes on or off. Factors that start transcription are called activators, and those that stop transcription are called repressors. The shape of the transcription factors determines whether it can bind to DNA, and can sometimes be altered by the binding of some molecules. This means the amount of some molecules in an environment can control the synthesis of proteins

Question 7

How do transcription factors act on eukaryotes?

Answer 7

Transcription factors bind to the DNA sites near the start of the target genes. They held repress or initiate the binding of RNA polymerase

Question 8

How does transcriptional level control act on prokaryotes?

Answer 8

This involves transcription factors binding to operons

Question 9

What is the structure of a gene?

Answer 9

A gene is located on the DNA strand downstream of a control reigon called a promotor

Question 10

What is a promotor?

Answer 10

The reigon where RNA polymerase binds to begin transcription

Question 11

What is an operon?

Answer 11

A section of DNA that contains a cluster of structural genes that are all transcribed, as well as control elements and sometimes a regulatory gene

Question 12

What are structural genes?

Answer 12

They code for useful proteins such as enzymes

Question 13

What are control elements?

Answer 13

Promotors and operators

Question 14

What are operators?

Answer 14

A DNA sequence thattranscription factors can bind to

Question 15

What are regulatory genes?

Answer 15

They code for an activator or repressor

Question 16

Explain the basic structure of a prokaryotic operon

Answer 16

They have a regulatory gene, control elements and structural genes

Question 17

What is the Lac operon?

Answer 17

It is found in E.coli and allows them to produce the enzymes needed for respiring lactose when present.

Question 18

What are the structural genes on the Lac operon?

Answer 18

. LacZ = B-galactosidase. This breaks down lactose into to glucose and galactose
. LacY = lactose permease. This increases the uptake of lactose
. LacA

Question 19

What happens in the lac operon when lactose is not present?

Answer 19

The regulatory gene (LacI) produces the lac repressor, which is a transcription factors and binds to the operator site when there is no lactose. This blocks RNA polymerase binding and therefore prevents transcription

Question 20

What happens in the lac operon when lactose is present?

Answer 20

When lactose is present, it binds to the repressor, changing the repressors shape do it can no longer bind to operator sites. RNA polymerase can then binds

Question 21

How can the lac operon be further regulated?

Answer 21

Due to the presence of the cAMP regulator protein, which when bound to the second messenger molecule cAMP is able to enhance the rate of RNA polymerase binding

Question 22

What is post transcriptional level control?

Answer 22

During transcription both introns and exons are copied into mRNA. This is called primary mRNA. Introns are removed from pre-mRNA and exons are joined to form mature mRNA. This is called splicing and takes place in the nucleus.
A modified gauntlet nucleotide is added to 5 prime and a polyadenylation sequence (AAAAA) is added to 3 prime.

Question 23

What are introns?

Answer 23

Non coding sequences

Question 24

What are exons?

Answer 24

Coding sequences

Question 25

What is post translational level control?

Answer 25

Some molecules dont function straight after synthesis and need to be activated. Some molecules that control protein activation work by binding to cells and triggering production of cyclic AMP inside the cell. cAMP then Activates proteins inside cells by altering their 3D structure

Question 26

What is an example of post translational control?

Answer 26

PKA (proteins kinase A) is an enzyme made of 4 subunits. When cAMP isn't present the 4 subunits are inactive. When binded, it causes the 3d shape to change, releasing active subunits.

Question 27

What are homeobox genes?

Answer 27

A group of genes which are involved in controlling the way embryos develop. They are 180 nucleotides.

Question 28

What are hox genes?

Answer 28

A specific type of homeobox gene that controls body plan development

Question 29

What is a body plan?

Answer 29

The general structure of an organism

Question 30

What do homeobox gene sequences on hox genes code for?

Answer 30

Proteins that are involved in regulating gene expression. This helps set up an organisms body plan so that everything is in the correct place. In this way they act as transcription factors

Question 31

What is a drosophila fruit flys body plan?

Answer 31

It has various body parts e.g the head, abdomen that are all arranged in a particular way

Question 32

What are homeobox genes in animals fungi and plants?

Answer 32

Highly conserved and very similar. This means teh sequences rarely changed during evaluation. This also means hox genes are found in nearly every animal so body plan development is controlled in similar ways

Question 33

Explain the development of the body plan of a drosophila fruit fly

Answer 33

Two hox genes clusters control this. One controls the development of the head and anterior thorax, and the other controls the development of the abdomen and posterior thorax

Question 34

How do hox genes control development?

Answer 34

Homeobox sequences on hox genes code for the homeodomain (60 amino acid sequence), which is a reigon of a protein. This can bind to specific sites on DNA, enabling the protein it is part of to work as a transcription factor. The protein binds to DNA at the start of developmental genes, activating or repressing transcription, therefore altering the production of proteins involved in the development of the body plan

Question 35

What do all body plans show?

Answer 35

Segmentation

Question 36

What forms in a developing embryo?

Answer 36

Blocks of tissue called somites

Question 37

What is within each somite?

Answer 37

Specific hox genes that will influence the gene expression in a way that allows the development of differentiated cells, tissues and organs

Question 38

Explain hox gene expression in humans

Answer 38

Hox gene expression in smites allows the development of structures that are complex. Which structures develop is determined by the location on the vertebral column where they originate

Question 39

What else is involved in body plans?

Answer 39

Apoptosis and mitosis

Question 40

What is apoptosis?

Answer 40

This is controlled cell death

Question 41

What are the stages of apoptosis?

Answer 41

- Enzymes inside the cell break down cell components - The cell shrinks and begins to fragment - Phagocytes engulf and digest the cell fragments

Question 42

What is the difference between what apoptosis and mitosis does for body plans?

Answer 42

Mitosis create the bulk of the body plans where as apoptosis refines the parts by removing unwanted structures

Question 43

What are examples of apoptosis occurring?

Answer 43

As tadpoles develop into frogs, their tails are removed. An excess of nerve cells are produced during development of the nervous system. Nerve cells that are not needed then undergo apoptosis

Question 44

What do genes that regulate the cell cycle and apoptosis respond to?

Answer 44

Internal and external stimuli E.g an internal stimuli could be DNA damage which would result in the expression of genes which cause the cell cycle to pause or apoptosis to occur E.g an external stimuli could be stress by lack of nutrients which could result in gene expression that prevents cells from undergoing mitosis. Another stimuli may be a pathogen, then causing apoptosis

Question 45

What is a DNA mutation?

Answer 45

A random change in the order of bases on the DNA strand. It is natural and occurs at very low levels but can be increased my mutating agents such as ionising radiation

Question 46

What to mutations generate?

Answer 46

New alleles

Question 47

What is a substitution?

Answer 47

Where one or more bases is swapped for another base. This may not have any impact as amino acids are degenerate

Question 48

What is a deletion or addition?

Answer 48

Where one or more bases is removed or added. This usually causes a frame shift

Question 49

What is a frame shift mutation?

Answer 49

This usually occurs due to an addition or deletion. The earlier a frames hint, the more amino acids are affected

Question 50

Why may a mutation have a neutral affect?

Answer 50

. The mutation changes a base but not the triplet code. This happens because amino acids are degenerate . The mutation produces a triplet code that codes for a different amino acid but that amino acid is chemically similar . The mutated triplet codes for an amino acid not involved in the proteins function

Question 51

What can mutations be?

Answer 51

Neutral, beneficial and harmful

Question 52

What are examples of harmful mutations

Answer 52

. Cystic fibrosis is cased by a deletion of 3 bases in the gene that codes for the CFTR (cystic fibrosis transmembrane conductance regulator). This folds incorrectly so its broken down leading to excess mucus . Mutations in the BRCA1 gene increases the risk of breast cancer. BRCA1 produces a protein that helps repair breaks in DNA. Mutations then lead to short proteins so it cant do its job leading to uncontrolled cell division

Question 53

What can harmful mutations also cause?

Answer 53

They can also affect whether or not a protein is produced. If a mutation occurs at the start of a gene so that RNA polymerase cannot bind, the protein coded cannot be made. This may cause harmful effects