Topic 7: Genetics, Population, Evolution and ecosystem

• Who is the presenter of the biology video?

  Miss Estri
• How long has Miss Estri been teaching biology?

  Over 10 years
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  Free exam question bundles
• What do Miss Estri's A Level notes cover?

  Key marking points for AQA papers
• What is the definition of genotype?

  Genetic constitution of an organism (all the different alleles an organism has)
• What does phenotype refer to?

  Expression of genes(genetic constitution) and environmental interaction
• What does homozygous mean?

  Same alleles for a single gene
• What does heterozygous mean?

  Different alleles for a single gene
• When is a recessive allele expressed?

  When no dominant allele is present
• What is codominance?

  Both alleles are equally dominant and expressed
• What is multiple alleles?

  More than two alleles for a single gene
• What is sex linkage?

  A gene located on the X chromosome
• What is epistasis?

  One gene modifies or masks another gene's expression
• What do monohybrid and dihybrid refer to?

  Types of genetic crosses
• What is the probability of a child having cystic fibrosis from two heterozygous parents?

  25%
• How do you calculate the probability of having a girl with cystic fibrosis?

  25% * 50% = 12.5%
• What colors can cows be in a codominant example?

  Red, white, or roan
• What is the probability of getting a red cow from two roan cows?

  25%
• What are the possible blood groups in humans?

  A, B, AB, or O
• What is the probability of having blood group A from parents with blood group AB and O?

  50%
• What causes color blindness?

  A recessive allele on the X chromosome
• What is the probability of children being colorblind from a non-color blind male and a female carrier?

  25%
• What does epistasis influence in genetics?

  Expression of another gene
• What are the two genes controlling color in Labradors?

  Gene for pigment and gene for color
• What is the expected phenotype ratio in a dihybrid cross?

  9:3:3:1
• What is autosomal linkage?

  Two genes on the same chromosome
• How does crossing over affect genetic ratios?

  It results in new combinations of alleles
• What happens to alleles during meiosis in autosomal linkage?

  They are inherited together
• What is the significance of the Punnett square in genetic crosses?

  It shows possible offspring genotypes
• What is the role of dominant alleles in genetic crosses?

  They mask the expression of recessive alleles
• What is the expected outcome when crossing a homozygous dominant with a homozygous recessive?

  All offspring will be heterozygous
• What is the purpose of identifying parental genotypes in genetic crosses?

  To determine possible offspring traits
• What is the significance of the gametes in genetic crosses?

  They determine the genetic makeup of offspring
• What is the expected phenotype ratio in a dihybrid cross with linked genes?

  It may differ from 9:3:3:1
• What is the effect of crossing over on gametes?

  It creates new allele combinations
• What is the relationship between linked genes and inheritance?

  Linked genes are inherited together
• What is the role of the Punnett square in predicting offspring traits?

  It helps visualize genetic combinations
• What is the expected outcome of a dihybrid cross with heterozygous parents?

  It will yield a variety of genotypes
• What is the significance of the phenotype in genetics?

  It reflects the expression of genes