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D. Genetic Processes · Genetic Processes

Genetic Processes: Unit Review

A1.1 A1.2 A1.3 A1.5 A1.6 A1.7 A1.8 A1.9 A1.10 A1.11 A1.12 A1.13 A2.1 A2.2 D1.1 D1.2 D2.1 D2.2 D2.3 D2.4 D3.1 D3.2 D3.3 D3.4 D3.5About 40 minutes
Learning goals
  • I can explain meiosis and how it produces variation.
  • I can solve monohybrid, dihybrid, incomplete dominance, codominance and sex-linked problems with Punnett squares and probability.
  • I can describe chromosomal and single-gene disorders and reproductive technologies.
  • I can evaluate advances in genetics and analyse their social and ethical issues.

Words to know

haploid / diploid
One set (n) / two sets (2n) of chromosomes.
allele
One version of a gene.
genotype / phenotype
The alleles an organism has / the trait you observe.
non-disjunction
Failure of chromosomes or chromatids to separate in meiosis.
recombinant DNA
DNA joined from two sources.

Let's review!

This unit took you from the DNA inside one nucleus to decisions that affect whole societies. You learned how meiosis makes haploid gametes and shuffles alleles; how Mendel's laws and Punnett squares predict offspring; how incomplete dominance, codominance, multiple alleles and sex linkage change the ratios; how to test data with chi-square; what happens when chromosomes or genes change; and how reproductive and genetic technologies are used and debated.

This review has a few questions from every lesson. Try each one, then press Show answer to check.

How to use this review

Do one or two sections at a time. For every cross: write a key, the parents' genotypes, their gametes, then the square (or product rule), then a sentence answer. Count chromosomes by counting centromeres. For every question you get wrong, write down why (vocabulary? wrong gametes? misread "son" vs "child"? arithmetic?) and go back to that lesson's worked examples. Finish with the 10-question quiz.

DNA, genes,chromosomes, allelesMeiosishaploid gametes, variationMendel's lawssegregation, assortmentTesting dataratios, chi-squareOther patternsco/incomplete, ABO, sex-linkedPunnett squaresand probabilityDisorderschromosomal and geneTechnologiesAI, IVF, cloning, rDNAAdvancesand ethics
The unit in one picture: from molecules (top row), to predicting inheritance (middle row), to health, technology and society (bottom row). Follow the arrows in the order you learned them.

DNA, Genes and Chromosomes: The Language of Heredity

1

What is the difference between a gene and an allele?

2

A species has 2n = 24. How many chromosomes are in its gametes, and how many pairs of homologues are in its body cells?

3

Homologous chromosomes or sister chromatids: which pair can carry different alleles? Why?

Meiosis: Two Divisions That Make Haploid Cells

1

Name what separates in anaphase I and in anaphase II.

2

A cell with 2n = 16 enters meiosis. How many tetrads form? How many chromosomes are in each cell after telophase II?

3

Why is meiosis I called the reduction division?

Why Siblings Differ: Meiosis, Variation and Gamete Formation

1

Name the three sources of genetic variation in sexual reproduction.

2

How many chromosome combinations can a gamete from an organism with 2n = 12 have (ignoring crossing over)?

3

Why does oogenesis produce one egg, not four?

Mendel's Peas and the Law of Segregation

1

State the law of segregation and the phase of meiosis that explains it.

2

Mendel's F2 for flower colour: 705 purple, 224 white. Calculate the ratio.

3

Can two plants with the same phenotype have different genotypes? Give an example.

Monohybrid Crosses: Punnett Squares, Probability and Test Crosses

1

Cross Gg × gg. Give the genotypic and phenotypic ratios.

2

A black guinea pig is test-crossed and has 3 black and 3 white pups. What is its genotype?

3

Two Aa parents have 4 offspring. What is the probability all 4 show the dominant phenotype?

Dihybrid Crosses and the Law of Independent Assortment

1

List the gametes of TtRr.

2

In TtRr × TtRr, what fraction show both recessive traits?

3

What ratio does TtRr × ttrr give?

4

Why don't linked genes follow the law of independent assortment?

Beyond Simple Dominance: Incomplete Dominance, Codominance and Multiple Alleles

1

Pink × white snapdragons: give the phenotypic ratio.

2

Distinguish incomplete dominance from codominance with one example each.

3

A type B mother (Iᴮi) and a type AB father have a child. List the possible blood types and their probabilities.

Sex-Linked Inheritance and Pedigrees

1

A carrier woman (XᴴXʰ) and a man with hemophilia (XʰY) have children. What fraction of their daughters will have hemophilia?

2

Why can't an X-linked trait pass from father to son?

3

In a pedigree, two unaffected parents have an affected daughter. What inheritance pattern does this show?

Investigating Crosses: Real and Simulated Data, Probability and Chi-Square

1

Observed 85 dominant and 15 recessive. Expected 3 : 1. Calculate χ² and conclude.

2

Offspring ratio 1 : 2 : 1 for phenotypes: what does it suggest?

3

Why should a geneticist count many offspring?

Chromosomal Disorders: Non-Disjunction and Karyotypes

1

Non-disjunction in meiosis II: how many of the four gametes are abnormal?

2

Give the karyotype notation for Turner syndrome and for Klinefelter syndrome.

3

What is a translocation?

Gene Mutations and Single-Gene Disorders

1

Why does deleting one base usually do more damage than substituting one base?

2

Give the inheritance pattern of cystic fibrosis, Huntington disease and hemophilia A.

3

Why is PKU included in newborn screening?

Reproductive Technologies and Genetic Diversity

1

Describe somatic cell nuclear transfer in two sentences.

2

Give one way artificial insemination can increase genetic diversity and one way it can decrease it.

3

What do restriction enzymes and ligase do?

Recent Advances in Genetics: Genomes, Gene Editing and Plant-Made Medicines

1

What did Lap-Chee Tsui's team discover in 1989, and why does it matter today?

2

What is the role of the guide RNA in CRISPR-Cas9?

3

Give one benefit and one challenge of producing insulin in safflower seeds.

Social and Ethical Issues in Genetics: Screening, Gene Therapy and IVF

1

Why is germ-line editing prohibited in Canada while somatic gene therapy is allowed?

2

What does the Genetic Non-Discrimination Act protect against?

3

List the five steps for analysing an ethical issue.

If the problem involves...use...One gene, complete dominance2 × 2 square; 3 : 1 or 1 : 1Two independent genes4 × 4 square or product rule; 9 : 3 : 3 : 1Heterozygote in between / shows bothsuperscripts (CᴿCᵂ); 1 : 2 : 1Blood typesIᴬ, Iᴮ, i; A and B codominantTrait on the X chromosomeXᴮ, Xᵇ, Y; sons get X from motherIs the ratio close enough?χ² = Σ (O − E)² ÷ E; df = categories − 1
Choosing the right tool for a genetics problem. Always write a key and the parents' gametes first.
Just for fun

Mendel spent years counting peas, flies have been helping geneticists for more than a century, and now you can solve a dihybrid cross in a few minutes. You've officially inherited the family business.

Check your understanding

Quiz

1.

Human sperm and egg cells each contain:

2.

Crossing over occurs during:

3.

Bb × Bb gives what phenotypic ratio (complete dominance)?

4.

What fraction of offspring of AaBb × AaBb show the dominant phenotype for both traits?

5.

Roan cattle (red and white hairs) show:

6.

A man with red-green colour vision deficiency and a homozygous normal woman have a son. The son's chance of having CVD is:

7.

A χ² value of 2.1 with 1 degree of freedom (critical value 3.84) means:

8.

Down syndrome is most often caused by:

9.

Which technology joins a human gene into a bacterial plasmid?

10.

Which is an example of a social or ethical issue in genetic screening?

For parents and teachers

How to use the results: match the kind of mistake to the lesson to revisit.

  • Confusing gene/allele, homologues/sister chromatids, or n/2n → DNA, Genes and Chromosomes.
  • Mixing up anaphase I and II, or chromosome/chromatid counts → Meiosis: Two Divisions.
  • Crossing over vs independent assortment, 2ⁿ combinations, sperm vs egg formation → Why Siblings Differ.
  • Genotype/phenotype, dominance, the 3 : 1 ratio → Mendel's Peas.
  • Errors in gametes, Punnett squares, probability, test crosses → Monohybrid Crosses.
  • Gametes for two genes, 9 : 3 : 3 : 1, product rule → Dihybrid Crosses.
  • Pink vs roan, ABO blood types → Beyond Simple Dominance.
  • X-linked crosses, "son" vs "child" probabilities, pedigree reading → Sex-Linked Inheritance and Pedigrees.
  • Expected numbers, chi-square, working backward → Investigating Crosses.
  • Non-disjunction, karyotypes, chromosomal conditions → Chromosomal Disorders.
  • Mutation types, single-gene disorders → Gene Mutations.
  • AI, IVF, cloning, recombinant DNA, diversity → Reproductive Technologies.
  • Evaluating advances → Recent Advances in Genetics; ethical reasoning, Canadian laws → Social and Ethical Issues.

Tip: Ask your teen to teach you one Punnett square and one meiosis stage from memory. Explaining is the best test of understanding.