cellular control - genetics

Question 1

define gene mutation

Answer 1

• a change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide
  -many mutations occur in non- coding sections of DNA so have no effect on the sequence

Question 2

three main ways that a mutation in the DNA base sequence can occur

Answer 2

-Insertion of one or more nucleotides
-Deletion of one or more nucleotides
-Substitution of one or more nucleotides

Question 3

insertion

Answer 3

-when a nucleotide is randomly inserted into the DNA sequence
-changes the triplet codes= rest of amino acid sequence is fucked

Question 4

deletion

Answer 4

-nucleotide is deleted, sequence and triplet codes are fucked

Question 5

substitution

Answer 5

-a nucleotide is randomly swapped
-only changes a specific triplet code

Question 6

3 forms of substitution mutations + description

Answer 6

silent mutation- does not alter the amino acid sequence as certain codons may code for same amino acid
missense mutation-alters a single amino acid in polypeptide chain e.g sickle cell anaemia
nonsense mutation-creates a premature stop codon (so stops translating the mRNA molecule into an amino acid sequence= affects the final protein structure e.g cystic fibrosis

Question 7

example of a beneficial mutation

Answer 7

production of melanin

Question 8

3 main types of regulatory mechanisms

Answer 8

Regulation at the transcriptional level (e.g lac operon)
Regulation at the post-transcriptional level
Regulation at the post-translational level

Question 9

structural gene

Answer 9

codes for a protein that has a function within a cell (e.g. enzymes

Question 10

regulatory genes

Answer 10

code for proteins (or various forms of RNA) that control the expression of structural genes

Question 11

what is an operon

Answer 11

: a group or a cluster of genes that are controlled by the same promoter
-prokaryotes use operons to control the expression of genes

Question 12

role of lac operon

Question 13

WATCH VIDEO ON LAC OPERON AND BE ABLE TO LABEL

Question 14

what are transcription factors

Answer 14

-proteins that bind to specific regions of DNA to control the transcription of genes
-eukaryotes also use transcription factors to express genes

Question 15

transcription factors mechanism

Answer 15

-bind to the promotor region which either allows of prevents transcription taking place
-presence of transcription factor will either increase or decrease rate of transcription

Question 16

name for coding and non coding sequences of DNA

Answer 16

Coding= exons, eventually translated into DNA
-Non coding= introns
-when transcription of a gene occurs, both exons and introns are transcribed=mRNA formed contains them

Question 17

splicing

Answer 17

-introns must be removed from the pre-mRNA molecule as they shouldnt be translated
-exons are then all fused together to form a continuous mRNA molecule called mature mRNA that is ready to be translated
-ENSURES ONLY THE CODING SECTIONS OF mRNA ARE USED TO FORM PROTEINS

Question 18

control at post transcriptional level

Answer 18

• polypeptides undergo modification in golgi or cytosol
  -some polypeptides require activation vis cAMP = can activate enzymes
  -

Question 19

homeobox genes

Answer 19

-responsible for the genetic control of the development of body plans in different organisms

Question 20

what is a homeobox

Answer 20

a DNA sequence that codes for a protein transcription factor

Question 21

hox genes WATCH VIDEO

Answer 21

-subset of homeobox genes
-determine the identity of embryonic body regions along the anterior-posterior axis (i.e. the head-tail axis)

Question 22

define mitosis and apoptosis

Answer 22

mitosis, identical cell division
apoptosis, natural cell death

Question 23

steps leading to cell death/ apoptosis

Answer 23

-DNA becomes denser and more highly packed
-nuclear envelope breaks down and chromatin condenses
-vesicles form that contain hydrolytic enzymes
-phagocytes engulf the cell via phagocytosis

Question 24

importance of mitosis and apoptosis in body plan development

Answer 24

-some cells that are produced (by mitosis) earlier on in development may no longer be needed
- e.g structures like fingers and toes first develop as a single combined unit and are then separated later via programmed cell death

Question 25

the 2 groups that control mitosis

Answer 25

-Proto-oncogenes are genes that stimulate cell division
-Tumour-suppressor genes are genes that reduce cell division can also stimulate apoptosis

Question 26

the role of cyclins and cyclin-dependant kinases in regulating the cell cycle

Answer 26

-Cyclins act as regulators
-CDKs act as catalysts (once activated by cyclins)
-e.g CDKs that have been activated by cyclins will catalyse the phosphorylation of particular target proteins, which can either activate or inactivate them

Question 27

internal factors that trigger apoptosis in cell cycle

Answer 27

-rreparable genetic damage
-RNA decay
-Internal biochemical changes that lead to cell changes or cellular injury (e.g. oxidative reactions)

Question 28

external factors that trigger apoptosis in cell cycle

Answer 28

-The presence of cell signalling molecules such as cytokines from the immune system, hormones and growth factors
-Viruses and bacteria, harmful pollutants or ultraviolet light