Free HSC Biology Flashcard Review

A reductional cell division producing four haploid gametes from one diploid parent cell. Two stages: Meiosis I (reductional) and Meiosis II (equational).

Homologous chromosomes pair up (synapsis) to form bivalents. Crossing over occurs between non-sister chromatids. Nuclear envelope breaks down.

Four genetically different haploid gametes produced from one diploid cell. Each has half the chromosome number. Non-identical due to crossing over and independent assortment.

Alleles of a gene segregate during gamete formation. Each gamete receives only one allele. During fertilisation, alleles recombine, restoring diploid state.

Alleles of different genes assort independently during gamete formation. Segregation of one gene does not influence another.

Genetic cross involving one gene with two alleles. Example: Aa x Aa produces 3:1 phenotypic ratio in F2.

Genetic cross involving two genes with two alleles each. Example: AaBb x AaBb produces 9:3:3:1 ratio if genes assort independently.

Genes on sex chromosomes (X or Y) with different inheritance patterns. Males (XY) hemizygous; females (XX) homozygous or heterozygous.

Both alleles fully expressed in heterozygote, showing both traits. Example: ABO blood type AB shows A and B antigens.

Type A: I^A I^A or I^A i. Type B: I^B I^B or I^B i. Type AB: I^A I^B. Type O: ii.

Square = male; Circle = female; Filled = affected; Half-filled = carrier. Horizontal line = couples; vertical line = offspring. Generations use Roman numerals.

Affected individuals usually have carrier parents. Both parents carry recessive allele. Trait can skip generations. Both sexes equally affected.

More affected males than females. Passes from carrier mothers to affected sons. Males cannot pass trait to sons. Affected females have affected fathers.

DNA helicase (unwinds), primase (makes RNA primers), DNA polymerase III (adds nucleotides), DNA ligase (seals Okazaki fragments).

New DNA has one original strand and one new strand. Original strands separate and each templates a complementary new strand.

mRNA synthesis from DNA template by RNA polymerase. Occurs in nucleus. mRNA carries genetic info to ribosomes.

Initiation: RNA polymerase binds promoter. Elongation: adds RNA nucleotides. Termination: stops at terminator; mRNA released.

Protein synthesis from mRNA at ribosome. tRNA transports amino acids. Codons match to tRNA anticodons.

Initiation: ribosome assembles at AUG start codon. Elongation: tRNA brings amino acids; peptide bonds form. Termination: stop codon signals end.

Triplet code: three nucleotides (codon) code for one amino acid. 64 codons: 61 for amino acids, 3 stops. Degenerate code.