Study Guide for the Genetics Unit Name ______

The Work of Gregor Mendel (section 10.1)

The students will be able to:

  • Explain who Gregor Mendel is.
  • Define the term “heredity”.
  • Define the term “genetics”.
  • Identify the parent generation in a cross.
  • Identify the F1 and F2 generations in a cross.
  • Explain why when Mendel crossed a purebred short pea plant with a purebred tall pea plant, the resulting F1 generation only had tall pea plants.
  • Explain why when Mendel allowed the F1 generation of all tall pea plants to self-pollinate, short pea plants reappeared in the F2 generation.
  • Define the term “gene”.
  • Define the term “allele”
  • Define the terms “dominant” and “recessive”.
  • Properly abbreviate the alleles that an individual possesses for a trait.
  • Define the terms “genotype” and “phenotype”.
  • Define the terms “homozygous” and “heterozygous”.
  • Identify the phenotype and genotype of different individuals for a given trait.
  • Explain what a Punnett Square is.
  • Use a Punnett Square to predict the possible offspring that may result from a cross.
  • Define the term “probability”.

·  Explain the role of probability in genetics.

Patterns of Heredity (sections 12.1 and 12.2)

The students will be able to:

  • Explain what a pedigree chart is.
  • Use a pedigree chart to track the presence of a trait in a family.
  • Identify the different symbols used in a pedigree chart.

Circle = female; Square = male, horizontal line connecting two = marriage

Line coming down from a marriage = offspring from the parents

Shaded in = affected by the trait half-shaded = carrier/heterozygous

  • Define the term “carrier”.

An individual that has the recessive gene but is not affected by its trait

  • Explain simple recessive inheritance.
  • Explain simple dominant inheritance.
  • Explain incomplete dominance.
  • Explain codominance.
  • Explain multiple phenotypes from multiple alleles.
  • Explain how the sex of an individual is determined.
  • Define the term “autosome”.
  • Define the term “sex chromosome”.
  • Explain sex-linked inheritance.
  • Define the term “sex-linked trait”.

Study Guide for Genetics - KEY

The Work of Gregor Mendel (section 10.1)

The students will be able to:

  • Explain who Gregor Mendel is.

“Father of genetics” – did experiments breeding pea plants to learn about heredity

  • Define the term “heredity”.

The study of how traits are passed on from one generation to the next

  • Define the term “genetics”.

Study of the actual genes that organisms possess and how they interact

  • Identify the parent generation in a cross.
  • Identify the F1 and F2 generations in a cross.
  • Explain why when Mendel crossed a purebred short pea plant with a purebred tall pea plant, the resulting F1 generation only had tall pea plants.

Tall is dominant over short and they were all heterozygous “Tt”

  • Explain why when Mendel allowed the F1 generation of all tall pea plants to self-pollinate, short pea plants reappeared in the F2 generation.

Crossing two heterozygotes will give you all three genotypes “TT” “Tt” & “tt”

  • Define the term “gene”.

A segment of DNA that codes for a single protein

  • Define the term “allele”

One possible variation of a gene; like a flavor that the gene can come in

  • Define the terms “dominant” and “recessive”.

Dominant alleles will be expressed over recessive alleles when they are both present

  • Properly abbreviate the alleles that an individual possesses for a trait.

Alleles are designated by the letter of the dominant trait

  • Define the terms “genotype” and “phenotype”.

Genotype tells you the genes that an organism has, phenotype tells you the trait

  • Define the terms “homozygous” and “heterozygous”.

Homozygous = two of the same allele (“TT” or “tt”)

heterozygous = two different alleles (“Tt”)

  • Identify the phenotype and genotype of different individuals for a given trait.

Homozygous dominant, heterozygous = dominant trait;

homozygous recessive = recessive trait

  • Explain what a Punnett Square is.

A tool for finding out what the probably outcomes of a genetic cross are

  • Use a Punnett Square to predict the possible offspring that may result from a cross.
  • Define the term “probability”.

The chances or odds that a certain outcome will happen, usually in a ratio or percentage

·  Explain the role of probability in genetics.

Using a punnett square, you can find the probability that a certain genetic outcome will occur, but it only tells you the probability, not a guarantee

Patterns of Heredity (sections 12.1 and 12.2)

The students will be able to:

  • Explain what a pedigree chart is.

A way of looking at the genes and traits that are passed down through a family tree

  • Use a pedigree chart to track the presence of a trait in a family.
  • Identify the different symbols used in a pedigree chart.

Circle = female; Square = male, horizontal line connecting two = marriage

Line coming down from a marriage = offspring from the parents

Shaded in = affected by the trait half-shaded = carrier/heterozygous

  • Define the term “carrier”.

An individual that has the recessive gene but is not affected by its trait

  • Explain simple recessive inheritance.

When a trait is recessive, an individual must have two copies of it in order to have the trait. If they have one recessive and one dominant allele, they will be a carrier.

(“aa” = affected; “Aa” = carrier – not affected)

  • Explain simple dominant inheritance.

When a trait is dominant, an individual can have one or two copies of it and be affected by the trait.

(“AA” or “Aa” = affected by the dominant trait)

  • Explain incomplete dominance.

When two alleles are both present, the outcome is a third phenotype which is a blend of the other two (“RR” = Red; “rr” = White; “Rr” = Pink)

  • Explain codominance.

When two alleles are both present, the outcome is both phenotypes are expressed together, but not blended. (“RR” = Red; “WW” = White; “RW” = both Red and White

  • Explain multiple phenotypes from multiple alleles.

Like blood types, sometimes there can be more than two alleles possible for a gene, which leads to a wider spectrum of possible outcomes

  • Explain how the sex of an individual is determined.

The sex chromosomes determine the sex of the offspring (XX = female, XY = male)

  • Define the term “autosome”.

A normal chromosome; in humans, one of the 22 other pairs

  • Define the term “sex chromosome”.

One of the chromosomes that determines gender; there are two possibilities: X & Y

  • Explain sex-linked inheritance.

If a trait is found on the X chromosome, males will only have one copy of it, so they can’t possibly be carriers. Males only need one copy of the recessive gene to have it.

  • Define the term “sex-linked trait”.

A trait whose gene is found on the X chromosome (or occasionally Y)