GN 301 Module 1: Basic Inheritance

Vocabulary

  • Phenotype: Describes the appearance of an individual for a trait
  • Genotype: Describes the alleles (forms of genes) that an individual has for a particular trait. Genotypes are indicated by alphabet abbreviations. Since each person has 2 copies of each gene, each person will have 2 letters representing their genotype.
  • Alleles: the various forms of genes
  • Dominant: The allele that is seen in the individual’s phenotype if an individual has two different alleles for a gene
  • Recessive: The allele that is not seen in the individual’s phenotype if an individual has two different alleles for a gene

Genetics in Humans

How many chromosomes are in a normal human gamete?

  • 23 chromosomes

Which gamete, the mother’s egg or the father’s sperm, determines the sex of the baby?

  • The ==father’s sperm determines the sex of the baby== because only sperm can carry a Y chromosome. The egg always carries an X chromosome, but ==the sperm can either carry an X or Y chromosome.== An XY combination creates a male and an XX combination creates a female.

How can the sex of the baby be determined prior to birth?

  • Using ultrasounds, bloodwork, and choosing sperm likely to have an X or Y chromosome. \n

Distinguish between monozygotic and dizygotic twins.

  • Monozygotic twins are identical. 1 sperm and 1 egg join together, and the embryo divides into 2 fetuses.
  • Meanwhile, dizygotic twins are fraternal. 2 eggs are fertilized at the same time (each with a different sperm) and make one fetus each. Unlike monozygotic twins, dizygotic twins run in families.

Approximately what proportion of your genes do you share with your full sibling?

  • Roughly 50%. \n

Give the name of a common genetic disorder

  • Down Syndrome, Huntington’s Disease, Cystic Fibrosis, Color Blindness, etc.

Cystic Fibrosis Example

Define Carrier:

  • Carriers have one copy of the cystic fibrosis allele and one copy of the normal allele

Cystic fibrosis is inherited in a recessive manner (so Cystic fibrosis would be ff)

  • The child will have a ÂĽ or a 25% chance of getting Cystic fibrosis if his parents are both carriers.

Mutation

Other than genetics, what can influence the phenotype of an individual?

  • The ==environment== can influence phenotype (height, weight, skin color, hair color, etc) beyond genetics.

Define Mutation

  • An ==incorrect copy of DNA==, or a change in the DNA sequence.

 \n What is the role of mutation in evolution?

  • Define ==Evolution==

    • The process by which organisms are assumed to have developed and diversified over time from their earlier forms.

  • Describe ==the role of mutation in evolution.==

    • Mutation serves as a form of adaptation in evolution. When a species would benefit from a mutation, organisms with that mutation are favored in the reproduction cycle so that the mutation gets copied to other members of the species. Therefore, mutations are essential for helping a species grow and adapt to new environments over time.