B6: Inheritance, variation and evolution

• What are the two types of reproduction?

  • Sexual reproduction
  • Asexual reproduction
• What is sexual reproduction?

  Involves fertilization of gametes
• What are the male and female gametes in animals?

  Sperm cell and egg cell
• What is a key feature of asexual reproduction?

  Involves one parent only
• What is the result of asexual reproduction?

  Genetically identical offspring (clones)
• How many chromosomes do humans have in body cells?

  46 chromosomes
• What is meiosis?

  A type of cell division for gametes
• What happens to chromosomes during meiosis?

  They are halved to form gametes
• What is the first stage of meiosis?

  Genetic information doubles
• How many gametes are produced at the end of meiosis?

  Four gametes
• What is the chromosome number in gametes?

  23 chromosomes
• What happens when an egg and sperm fuse?

  They form a fertilized egg with 46 chromosomes
• What is the structure of DNA?

  Two strands forming a double helix
• What is a gene?

  A section of DNA coding for proteins
• What is a genome?

  The entire genetic material of an organism
• How are scientists using the human genome?

  To understand inherited disorders better
• What are alleles?

  Different forms of a gene
• What is a phenotype?

  Physical characteristics of an organism
• What is a genotype?

  The alleles an organism has
• What does homozygous mean?

  Having two identical alleles
• What does heterozygous mean?

  Having two different alleles
• What are dominant alleles?

  Alleles always expressed in phenotype
• What are recessive alleles?

  Alleles expressed only if two copies exist
• How are dominant and recessive alleles represented?

  Capital letters for dominant, lowercase for recessive
• What is a Punnett square used for?

  To predict offspring genotypes and phenotypes
• What is the phenotype of a child with genotype Big B little b?

  Brown eyes
• What is the expected ratio of genotypes from two heterozygous parents?

  1:2:1 ratio
• What is the expected phenotype ratio from two heterozygous parents?

  3:1 ratio
• What is the probability of a child having blue eyes from a heterozygous brown-eyed parent?

  25% probability
• What is the probability of a child having brown eyes from a heterozygous brown-eyed parent?

  75% probability
• What is the expected ratio of smooth to wrinkled offspring from two heterozygous pea plants?

  3:1 ratio
• What is the expected genotype ratio from two heterozygous pea plants?

  1:2:1 ratio
• What is the phenotype of offspring with genotype little s little s?

  Wrinkled phenotype
• What is the genotype of offspring with smooth phenotype from a heterozygous cross?

  Big S little s or Big S Big S
• What is the expected phenotype ratio from a cross of two heterozygous smooth pea plants?

  3 smooth: 1 wrinkled
• What are the genotypes of the offspring in the example given?

  1 big S big S, 2 big S little s, 1 little s little s
• What percentage of the offspring have the genotype big S little s?

  50%
• How can the order of genotypes affect the ratio presented?

  The ratio may appear in a different order
• What phenotype do offspring with at least one big S allele exhibit?

  They are smooth
• What is the phenotype ratio of smooth to wrinkled offspring?

  3 to 1