L7 ; A LEVEL REVISION - genes & inheritance

Question 1

mutations def, caused by? , e.g.

Answer 1

• change in the base sequence of DNA
• errors in replicating DNA
• deletion, insertion, substitution, duplication, inversion (bases are reversed)

Question 2

order of DNA base sequences determines;

Answer 2

order of AA

Question 3

DEFINITIONS

• gene
• allele
• genotype
• phenotype
• dominant
• recessive

Answer 3

gene; base sequences of DNA molecule - codes for a protein, results in a characteristic

allele; different version of the genes; homozygote (same alleles) or herterozygote (diff alleles) check this

• differnet versions of genes i.e. alleles have slightly altered base sequences
• codes for variation of same characteristic e.g. being eye colour - brown vs blue

genotype; the alleles a person has

phenotype; characteristic an organism displays due to
the genotype

dominant; an allele that appears in the phenotype even when theres only one copy
capital letters

recessive; an allele that appears in the phenotype ONLY when there are 2 copies
small letters

Question 4

incomplete dominance

homozygote

heterozygote

carrier

co dominance

Answer 4

when the trait form the dominant allele isn’t completely shown over the recessive alley
- thus both allele influence phenotype

HOMOZ; organism that carries 2 copies of the same gene for a certain characteristic

HETEROZ; organism that carries 2 different alleles for a certain characteristic

carrier; if a recessive allele has a disease; a carrier is a person who has a dominant & recessive allele (heterozygous)
the carrier i.e. person does not have the disease but has the alleles that carry

co dominance ; when one gene is not dominant over another