Inheritance, Gene Exp, Mutations & Editing

Question 1

Distinguish between sex-linked inheritance and autosomal inheritance in humans (3)

Answer 1

• sex-linked genes are usually found on the X chromosome from the 23rd, sex chromosome, pair WHILE autosomal genes are found on chromosomes 1-22
• inheritance is dependent on the biological sex of the offspring in sex-linked BUT not in non-sex linked
• biological males receive one allele for sex-linked characteristics, and biological females receive two alleles for sex-linked characteristics (when carried on the X chromosome), BUT biological males and females both receive two alleles for characteristics controlled by genes on autosomes
  -​ in sex-linked inheritance, biological females can be carriers for a trait, and biological males cannot be carriers, WHILE in autosomal inheritance, both biological sexes can be carriers

Question 2

Outline how polygenic traits can show a normal distribution (4)

Answer 2

• traits influenced by 2 or more genes
• the more genes responsible, the wider possibilities for phenotypes
• broad continuous range of variation of phenotypes
• where most organisms lie in middle as there are more likely to happen due to dominance
• shows curve

Question 3

Explain why expected and observed Mendelian ratios may differ. (4)

Answer 3

• mendelian ratios show proportions of genotypes from a cross
• may differ to observed because of mutations
• because of linked genes not segregating independently
• interactions with environment, since it can alter observed phenotype

Question 4

Outline five causes of gene mutations. (5)

Answer 4

• during DNA replication, mistakes can occur
• Error in proofreading
• virus and integrate their genetic material
• chemical mutagens
• physical damage to DNA
• exposure to carcinogens

Question 5

Describe the roles of non-coding DNA sequences (5)

Answer 5

• do not code for polypeptides
• Promoters regulate gene expression by telling RNA polymerase where to bind
• enhancers and silencers can either encourage of inhibit transcription when factors attach
• telomeres are caps at end of chromosomes to mantain stability and preserve it
• some code for rRNA nad tRNA

Question 6

Describe the role of DNA-binding proteins in gene expression. (5)

Answer 6

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