3.1 Genes

Question 1

What characteristics do genes code for?

Answer 1

Physical, behavioural, physiological features

Question 2

What discrete structure is DNA packaged and organised into?

Answer 2

Chromosomes

Question 3

What is a gene?

Answer 3

Sequence of DNA that encodes for a specific trait

Question 4

What is the position of a gene on a particular chromosome called?

Answer 4

Loci

Question 5

What are alleles?

Answer 5

Alternative forms of a gene that encodes different variations of a specific trait

Question 6

What is a gene mutation?

Answer 6

A change in the nucleotide sequence of a section of DNA coding for a specific trait

Question 7

What 3 things can mutations be?

Answer 7

Beneficial - change in the gene sequence (missense mutations) to create new variations of traits
Detrimental - truncate the gene sequence (nonsense mutations) to abrogate the normal function of a trait
Neutral - have no effect on the functioning of the specific feature (silent mutations)

Question 8

What is an example of a disorder caused by gene mutations?

Answer 8

Sickle cell anemia
(From a base substitution (single base was changed))

Question 9

what causes sickle cell anemia? (4 )

Answer 9

Results from a change to the 6th codon for the beta chain of haemoglobin
DNA - DNA sequence changed from GAG to GTG on the non-transcribed strand
mRNA - mRNA sequence changed from GAG to GUG at the 6th codon position
Polypeptide - 6th amino acid for the beta chain of haemoglobin is changes form glutamic acid to valine (Glu to Val)

Question 10

What occurs with sickle cell anemia? (2)

Answer 10

Amino acid changes (Glu->Val) alters the structure of haemoglobin, causing it to form insoluble fibrous stands
-> insoluble haemoglobin cannot carry oxygen as effectively causing the individual to be constantly tired

Question 11

What doe the formation of the fibrous haemoglobin do to the shape of the red blood cell in sickle cell anemia? (3)

Answer 11

Changed the shape to sickle cell
- sickle cells may form clots within the capillaries blocking blood supply to vital organs and causing health issues
- sickle cells are also destroyed more rapidly than normal cells, leading to a low red blood cell count (anaemia)

Question 12

what is the genome?

Answer 12

totality of genetic information of a cell organism or organelle
(includes all genes as well as non-coding DNA sequences eg. introns, promoters, STR)

Question 13

what does the human genome consists of? (3)

Answer 13

• 46 chromsomes
• 3 billion base pairs
• 21,000 genes

Question 14

what outcomes did the human genome project lead to? (4)

Answer 14

• mapping - established the No, location sie and sequence of human gene
• screening - allowed for the production of specific gene probes to detect sufferers and carriers of genetic diseases
• medicine - discovery of new proteins lead to improved treatments
• ancestry - comparisons with other genomes have provided insight into the origins, evolution and migratory patterns of man

Question 15

how is the number of different genes in a genome predicted?

Answer 15

• identifying regions may include expressed sequence tags (EST) or sequences that are homologous to known genes

Question 16

what makes the accurate counts of unique gene numbers very difficult? (2 things)

Answer 16

presence of pseudogenes and transposons