topic 7: genetics, populations, evolution and ecosystems

• What does phenotype refer to?

  Expression of genes and environment 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 another gene's expression
• What do monohybrid and dihybrid refer to?

  Types of genetic crosses
• What is a monohybrid cross?

  Inheritance of one gene
• What is a dihybrid cross?

  Inheritance of two genes at a time
• How do you represent a monohybrid cross?

  Using capital for dominant, lowercase for recessive
• How are codominant alleles represented?

  Base letter for gene, superscript for alleles
• What does epistasis influence?

  Expression of another gene
• What are the three colors of Labradors?

  Black, brown, and yellow
• What does Gene One control in Labradors?

  Whether pigment will be expressed
• What does Gene Two control in Labradors?

  Color of the expressed pigment
• What is the expected outcome of a cross between two homozygous dominant Labradors?

  All offspring will be black
• What is the ratio of offspring in a dihybrid cross with two heterozygous parents?

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

  Two genes on the same chromosome
• What happens during crossing over?

  New combinations of alleles are formed
• How does autosomal linkage affect inheritance?

  Genes are inherited together
• What is the expected outcome of a dihybrid cross with linked genes?

  Different ratios than expected
• What does it mean for alleles to be linked on the same chromosome?

  They must be inherited together during meiosis.
• How are gametes formed during meiosis?

  Whole chromosomes are pulled to create gametes.
• What types of gametes can be formed from linked alleles for the Y and R genes?

  Two dominant and two recessive alleles.
• What is the expected phenotypic ratio in a dihybrid cross without linkage?

  A 9:3:3:1 ratio.
• How does autosomal linkage affect the expected phenotypic ratio?

  It can lead to a 3:1 ratio instead of 9:3:3:1.
• What role does crossing over play in genetic variation?

  It creates new combinations of gametes.
• What is the purpose of the chi-squared statistic?

  To investigate differences in frequencies.
• What does the null hypothesis state in a chi-squared test?

  There is no significant difference between frequencies.
• How do you convert a ratio from a Punnett square into expected frequencies?

  By calculating based on total offspring.
• What is the expected frequency of purple and yellow corn in a 3:1 ratio?

  25.5 purple and 8.5 yellow.
• What is the significance of the degrees of freedom in a chi-squared test?

  It is the number of categories minus one.
• What does it mean if the calculated chi-squared value is less than the critical value?

  Accept the null hypothesis; no significant difference.
• What is the Hardy-Weinberg principle used for?

  To predict allele frequencies in a population.
• What does the gene pool represent?

  All alleles of all genes in a population.
• How is allele frequency defined?

  Proportion of an allele within the gene pool.
• What does the Hardy-Weinberg equation calculate?

  Allele and genotype frequencies in a population.
• How do you find the proportion of carriers using the Hardy-Weinberg equation?

  Calculate using 2pq for heterozygous individuals.