inheritance

Question 1

what is a gene

Answer 1

specific set of nucleotides that codes for the synthesis one one polypeptide

Question 2

what is an allele

Answer 2

alternative form of a gene, slightly diff nucleotide sequence that is in the same gene loci on a pair of homologous chromosomes

Question 3

what is a genotype

Answer 3

combination of alleles of genes in an organism

Question 4

what is a phenotype

Answer 4

OBSERVABLE physical traits of an organism
result of the expression of all the genotypes in the organism + environmental factors

Question 5

what is dominant

Answer 5

the allele of a gene that is expressed in both the homozygote and a heterozygote

Question 6

what is recessive

Answer 6

allele of a gene only expressed in a homozygote. (masked expression my the dominant allele)

Question 7

homozygous

Answer 7

the organism having the genotype with the same alleles at the gene loci on a pari of homologous chromosomes

Question 8

heterozygous

Answer 8

the organism having 2 different alleles of the same gene at a particular locus on a pair of homologous chromosomes

Question 9

what is a monohybrid test cross for?

Answer 9

determine if the organism is heterozygous or homozygous

Question 10

examples of sex linked inheritance

Answer 10

red green colour blindness (x linked recessive)
haemophilia (x linked recessive)

Question 11

describe someone with haemophilia

Answer 11

forming a blood clot involves many proteins. the DEFICIENCY of the proteins result in excessive bleeding
- excessive bleeding
- female will die when she reaches puberty
- linked recessive
- males have a higher probability of having it than females (if they inherit the x linked recessive gene from their mother they do not have a corresponding gene in the y chromosome to mask the recessive allele) they only need ONE copy of the defective allele
- females need TWO copies of the defective allele

Question 12

characteristics of a pedigree analysis: autosomal dominant

Answer 12

• equal probability of being affected and unaffected
• present in every generation
• if the offspring if affected, one of its parents is affected
• (prove it isn’t sex linked): the affected father with an unaffected mother has an affected son

huddington’s disease

Question 13

characteristics of pedigree analysis: autosomal recessive

Answer 13

• unaffected parents can have affected offspring
• lower probability of being affacted (rare)
  sickle cell aneamia, albinism

Question 14

characteristics of pedigree analysis: x linked recessive

Answer 14

• if a mother is affected, all her sone will be affected
• phenotypically normal parents have affected sons (mother is a carrier)
• more males than females affected

Question 15

what are the types of mutations?

Answer 15

• change to nucleotide sequence
• change to structure of chromosome
• change the number of chromosomes

Question 16

example of a beneficial mutation

Answer 16

• mutation in the immunoglobin gene allows for a ponetntial to generate antibodies of high affinity towards many antigens
• important in the rise of viruses with novel antigens like sars

Question 17

what are mutagens

Answer 17

chemical or physical agents that cause mutations

Question 18

examples of mutagens

Answer 18

chemical carcinogens: mustard gas, caffeine, certain constituents of tobacco drugs, formaldehyde, pesticides
particles: alpha and beta particles, neutrons, cosmis radiation
high energy radiation: x ray, gamma ray, uv light

Question 19

sickle cell anaemia

Answer 19

Mutation of the beta globin gene
One defective copy also has the sickle cell trait
HbA is a protein and transports oxygen (normal), made up of 2 alpha and 2 beta polypeptide chains

However, HbS is formed instead due to the mutation of the Beta global gene.
Base pari substitution from thymine to adenine. Change in the mRNA codon from GAG to GUG
Hydrophilic glutamic acid becomes hydrophobic valine
Polypeptide folds DIFFERENTLY, exposing hydrophobic patch

When the HbS releases oxygen, the hydrophobic patch is exposed, polymerisation ==> rigid rod like fibres, sickle shaped
Distorts the bioncave shape

Impacts: inefficient in transporting oxygen, clump and clog small capillaries
Insufficient oxygen to organs, organ failure
They have a shorter life span, haemolyse easily, resulting in anaemia
Accumulate in the spleen for destruction, spleen enlargement

Question 20

down syndrome type of mutation and how?

Answer 20

• chromosomal abbreviation
• addition of chromosome 21 (somatic)

Question 21

what is discontinous variation and exmple

Answer 21

phenytypic variation with 2 or more distinct, non overlapping classes with no intermediates in between them. usually controlled by 1 gene and not affcted by environmental factors

• blood group and sex

Question 22

what happens during natural selection

Answer 22

there are a range of phenotypes
- organisms with the phenotypes best suited to the envronment will be selected for
- increase in frequency of those alleles over generations

Question 23

how to answer natural selection questions?

Answer 23

the phenotype before was more common as___
however after the ___
the organisms could ____
the allele frequency shifted in favour of the allele conferring rhe dark colour