Genes and alleles

Question 1

genes

Answer 1

• chromatid made up of one helical DNA molecule
• DNA molecule made up of a series of genes
• defined as a section of DNA (series of nucleotides/bases) controlling hereditary characteristics
• basic unit of heredity in living organisms

Question 2

gene points

Answer 2

• each chromosome between several hundred and several thousand genes
• somatic cells have exact copy of genes in the organism
• 2 kind of chromosomes (maternal and paternal), each cell contains two of each kind of gene (before replication) known as alleles
• gene pool is set of all genes or genetic information, the greater the pool the greater the diversity therefore a higher chance of survival

Question 3

how active are genes?

Answer 3

• only genes needed are activated
• different genes activated in different cells give them particular cell type characteristics
• some useful for early development of embryo thereafter not used
• some are ‘housekeeping genes’ making specific proteins
• 98% are non-coding genes
• hox genes are master control genes
• epigenetics is the control of genes (applies to HGP)

Question 4

alleles

Answer 4

• genes that control different versions of a trait / characteristic found in the same locus (position) on homologous chromosomes

Question 5

How are alleles represented?

Answer 5

• represented by means of letters
• capital (dominant)
• lower case (recessive)

Question 6

How are alleles passed from parent to offspring?

Answer 6

• by chromosomes in the gametes

- made by meiosis in sex organs

Question 7

summary

Answer 7

• somatic cells = diploid
• a pair of homologous chromosomes
• two alleles may be same or different

Question 8

what happens to the gametes?

Answer 8

• during fertilisation, male gamete fuses to female gamete and their alleles to form diploid zygote
• mitosis occurs forming new organism
• same set of chromosomes and alleles as zygote