6.1 Genetics of Living Systems

Question 1

What is a codon ?

Answer 1

Each amino acid in a protein id coded for by a sequence of 3 nucleotide bases on mRNA called a codon.

Question 2

What is degenerate ?

Answer 2

More codon than amino acids so different codons code for the same amino acid.

Question 3

What is non-overlapping ?

Answer 3

Codes for 1 codon at a time for 3 bases.

Question 4

What is the universal code ?

Answer 4

All organisms have DNA.

Question 5

What is a mutation ?

Answer 5

A mutation is a change in the sequence of bases in dan. This can disrupt the protein synthesis. It is caused by insertion, deletion or substitution.

Question 6

What is substitution ?

Answer 6

Swapping base changes codon. May change amino acid leading to a change in primary structure, but same amino acid may be brought as DNA is degenerate.

Question 7

What is insertion or deletion ?

Answer 7

Insert or deletion of one or more bases. Leads to frameshift mutation buy shifting the reading frame of bases. This changes every successive codon from the point of mutation.

Question 8

What is a mutagen ?

Answer 8

Physical or chemical or biological agent that causes mutations.

Question 9

What are silent mutations ?

Answer 9

They do not change proteins so has no overall impact to organism.

Question 10

What is a nonsense mutation ?

Answer 10

Change in codon to a stop codon. Protein is shortened and is usually non-functional.

Question 11

What is a missense mutation ?

Answer 11

Results in the change of amino acid into primary structure. Result depends on the amino acid so can be severe or minimal.

Question 12

What is deletion ?

Answer 12

Selection of chromosome breaks off and is lost within a cell.

Question 13

What is duplication ?

Answer 13

Sections of DNA are duplicated.

Question 14

What is translocation ?

Answer 14

Section of one chromosome breaks off and joins another non-homologous chromosome.

Question 15

What is inversion ?

Answer 15

Section of chromosome breaks off, is reversed and joins back on to the chromosome.

Question 16

What is neutral affect of mutation ?

Answer 16

Caused by silent mutations, where normal proteins are still synthesised.

Question 17

What is the harmful effect of mutations ?

Answer 17

Proteins are not synthesised or are non-functional.

Question 18

What is the effect of beneficial mutations ?

Answer 18

Proteins synthesised with new and useful characteristics.

Question 19

What is transcriptional gene regulation ?

Answer 19

Genes are turned on or off.

Question 20

What is post- transcriptional gene regulation ?

Answer 20

mRNA can be modified which regulated translation and proteins used.

Question 21

What is translational gene regulation ?

Answer 21

Genes can be stopped or started.

Question 22

What is post-translational gene regulation ?

Answer 22

Proteins modified after synthesis which changes the function.

Question 23

What is chromatin remodelling ?

Answer 23

Heterochromatin is tightly wound DNA causing chromosomes to be visible. Euchromatin is loosely wound DNA present in DNA. Transcription of genes is not possible when DNA is tightly wound because RNA polymerase cannot access genes.

Question 24

What is histone modification ?

Answer 24

DNA coils around histones because they are positively charged. Addition of acetyl or phosphate groups reduces the positive charge of histones so DNA coils less tightly allowing certain genes to be transcribed. Addition of methyl groups makes histones bind more tightly preventing transcription.

Question 25

What Is the transcription factor ?

Answer 25

Binds to inhibitor to stop transcription. Hormones also bind to release the inhibitor and to bind to the promoter.

Question 26

What is an operon ?

Answer 26

An operon is a group of genes that are under control of the same regulatory mechanism and are expressed at the same time.

Question 27

What is Lac Operon ?

Answer 27

Group of 3 genes involved in the metabolism of lactose. They are structural genes as they are transcribed onto a single long molecule of mRNA. Regulatory gene is located near to operon coding for repressor protein that prevents transcription of structural genes in absence of lactose. binds to operator to prevent RNA polymerase.

Question 28

What is cyclic AMP ?

Answer 28

Binding of cAMP increases rate of transcription when bound o CRP. Transport of glucose in E Coli decreases levels of cAMP, reducing transcription.

Question 29

What is RNA processing ?

Answer 29

Product of transcription is a precursor molecule, which is modifies forming mature mRNA before binding to a ribosome. A cap is added to help stabilise mRNA and delay degradation.

Question 30

What is degradtion of mRNA ?

Answer 30

More resistant the molecule, the longer it lasts in the cytoplasm so the more protein synthesised.

Question 31

What are protein kinases ?

Answer 31

Enzymes that catalyse addition of phosphate groups to proteins. Addition of phosphate groups changes tertiary structure and function of protein. Many enzymes are activated by phosphorylation. They are important regulators of cell activity. Often activated by secondary messenger cAMP.

Question 32

What is morphogenesis ?

Answer 32

Regulation of pattern of anatomical development.

Question 33

What are homeobox genes ?

Answer 33

Group of genes which all contain a homeobox, which is a section of DNA coding for protein 60 amino acids long. They are regulatory genes.

Question 34

What are Hox genes ?

Answer 34

One group of homeobox genes only present in animals responsible for correct positioning go body parts. Order in which genes appear along the chromosome in order in which their effects are expressed in the organism.

Question 35

How are body plans represented throughout the body ?

Answer 35

Represented as cross-sections through organism showing fundamental arrangement of tissue layers. -Diploblastic = 2 primary tissue layers. -Triploblastic = 3 primary tissue layers.

Question 36

What are somites ?

Answer 36

Individual vertabrae have all developed from segments in embryo called somites, directed by the Hot genes to develop in a particular way.

Question 37

What is apoptosis ?

Answer 37

Shaping of body parts by removing unwanted cells and tissues. Cells undergoing apoptosis release chemical signals which stimulate mitosis and cell proliferation leading to the remodelling of tissues.

Question 38

How does apoptosis work ?

Answer 38

Nucleus condenses causing cell to shrink. Nucleus fragments and cell splits forming apoptic bodies. Apoptic bodies are engulfed by phagocytes. Can be influenced by environment from both internal and external factors.

Question 39

Factors effective expression of genes ?

Answer 39

Stress, temperature, light intensity, hormones, drugs such as thalidomide.