Genetics: Mitosis and Sex Linkage

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Questions and Answers

What is the purpose of a test cross in genetics?

To determine the genotype of a dominant phenotype individual (correct)

To determine an individual's phenotype

To analyze the offspring ratios of a cross

To identify mutations in the alleles

What does Mendel's Law of Equal Segregation state?

Alleles assort independently during gamete formation

Phenotypes dominate over genotypes in inheritance

Homozygous alleles produce more offspring variations

Each allele of a gene segregates equally into gametes (correct)

How is a chromatid defined in the context of cell division?

A pair of homologous chromosomes

A chromosome that has not undergone meiosis

A single strand of DNA before replication

A replicated chromosome consisting of two identical sister strands (correct)

In a Punnett square demonstrating a cross between G/G and g/g, what are the expected offspring phenotypes in F1?

All yellow phenotype offspring Signup and view all the answers

Which term describes the number of sets of chromosomes in an organism?

Ploidy number Signup and view all the answers

What does Mendel's Law of Segregation state?

Alleles separate during gamete formation. Signup and view all the answers

Which of the following best describes a Punnett Square?

A tool to predict the percent chance of offspring's traits. Signup and view all the answers

The chromosomal theory of inheritance states that:

Genes are inherited on chromosomes and are located in the nucleus. Signup and view all the answers

In pedigree analysis, a square symbol represents which of the following?

An unaffected male. Signup and view all the answers

During which phase of cell division do homologous chromosomes segregate?

Prophase I of meiosis. Signup and view all the answers

What is the expected outcome of a Punnett square analysis involving two heterozygous parents (e.g., Aa x Aa)?

There will be a 1:2:1 ratio of genotypes. Signup and view all the answers

Which statement correctly reflects Mendel's Law of Equal Segregation?

Gametes receive one allele from each pair during gamete formation. Signup and view all the answers

What was a significant contribution of Sutton and Boveri to the Chromosomal Theory of Inheritance?

were not associated with chromosomes. Signup and view all the answers

In humans, what pattern is indicative of an autosomal recessive trait in pedigree analysis?

The trait can appear to skip generations. Signup and view all the answers

Which condition best describes a homogametic sex in humans?

A female with XX chromosomes. Signup and view all the answers

What does a reciprocal cross test for in genetics?

The inheritance pattern of sex-linked traits. Signup and view all the answers

What is a characteristic of an autosomal dominant pedigree?

There is no skipping of generations. Signup and view all the answers

During which process do non-sister chromatids exchange genetic material?

Meiosis I Signup and view all the answers

Study Notes

Cell Division: Mitosis

Non-sister chromatids can be either same (homozygotes) or different (heterozygotes)

Mendel’s Law of Equal Segregation

Mendel’s Law of Equal Segregation was refined with the discovery of chromosomes

Chromosomal Theory of Inheritance

Sutton and Boveri proposed that Mendel's "particles" were associated with chromosomes
They observed the separation of chromosomes during meiosis under a microscope
Morgan was initially skeptical, but later proved their theory correct

Sex Linkage

Sex chromosomes are non-autosomes
One sex may not have a pair of similar sex chromosomes, while the other does.
Homogametic individuals have matching pairs of sex chromosomes (ex. XX)
Heterogametic individuals do not have a matching pair (ex. XY)

Testing for Sex Linkage – Reciprocal Cross

Alleles:
- w = mutant (white)
- - = wild-type (Red)
Reciprocal Cross:
- Parental generation (P0): X+/X+ x Xw/Y
- First filial generation (F1): X+/Xw x X+/Y
- Second filial generation (F2): X+/X+, X+/Xw, X+/Y, Xw/Y, X+/Xw, Xw/Xw, X+/Y, Xw/Y

Human Pedigree Analysis

Pedigree analysis is used to study family trees and medical records, as ethically testing humans is not possible
Propositus is the first member of a family who comes to the attention of a geneticist, usually due to a disease
Pedigree analysis can be used to look for patterns suggesting dominance and sex-linkage, as it may not show 3:1 and 1:1 ratios due to small family size

Autosomal Recessive Pedigree

Unaffected parents (carriers) can have offspring with the disease
If both parents have the trait, all children will have it
The likelihood of males and females showing the trait is equal, although the overall numbers may not be equal

Autosomal Dominant Pedigree

Each affected individual must have at least one affected parent
Both males and females can transmit the mutant allele to both sons and daughters with equal probability

Genotype, Phenotype, and Allele Combinations

Genotype: The allele combinations expressed as symbols, where the symbol indicates the mutant or recessive phenotype
Alleles: Different forms of the same gene are represented by the same letter, but different cases (ex. G/g, where G is dominant and g is recessive)

Punnett Square

A tool used to predict the genotype and phenotype of offspring based on the parental genotypes, like in the case of a cross between yellow (G/G) and green (g/g) parents, where the F1 generation is all yellow (G/g)

Test Cross

A cross used to determine the genotype of an individual with a dominant phenotype
The individual with the unknown genotype is crossed with a homozygous recessive tester (g/g) to determine if the individual is homozygous dominant (G/G) or heterozygous (G/g)
If the individual is homozygous dominant, all offspring will express the dominant phenotype
If the individual is heterozygous, then the offspring will show a 1:1 ratio of dominant to the recessive phenotype

Mendel's Law of Equal Segregation

This law describes the separation of two alleles of a gene during gamete formation, so each gamete receives one allele

Parts of a Chromosome

Centromere: The region where sister chromatids attach
Telomeres: The ends of a chromosome
P arm: The shorter arm of a chromosome
Q arm: The longer arm of a chromosome
Metacentric: The centromere is located in the middle of the chromosome.
Acrocentric: The centromere is located close to one end of the chromosome.
Telocentric: The centromere is located at the very end of the chromosome.

Ploidy Number (n)

Refers to the number of sets of chromosomes, not the total number
Haploid (n): One set of chromosomes
Diploid (2n): Two sets of chromosomes
Triploid (3n), Tetraploid (4n), etc.

Chromosome vs. Chromatid

Before mitosis or meiosis, DNA replication occurs to form a dyad:
- One chromosome, one chromatid
After S phase:
- One chromosome, two sister chromatids
After mitosis/meiosis II:
- One chromosome, one chromatid

Sister Chromatids

Have the exact same alleles
Formed through DNA replication during S phase

BIOL 311: Principles of Genetics

Focuses on:
- Understanding genetic principles
- Applying these principles to solve problems
- Developing a vocabulary for understanding genetics
Topics:
- Classical Genetics:
  - Single gene inheritance
  - Independent assortment of genes
  - Genetic linkage
  - Gene interactions
  - Recombination and large chromosomal rearrangements
  - Bacterial and viral genetics
- Molecular Genetics:
  - DNA replication and PCR
  - DNA variation and sequencing
  - Gene structure, transcription, and translation
  - Prokaryotic gene regulation
  - Eukaryotic gene regulation
  - Cloning, restriction mapping, and CRISPR
  - Genetics of Development

Tips for Success in Biology 311

Attend class regularly and be engaged
Complete textbook readings, including Achieve adaptive readings and quizzes
Practice problems and assignments multiple times
Prepare for labs in advance by reading and understanding the purpose
Check D2L regularly for additional resources

Learning Strategies

Understand your preferred learning style and optimize for that
Engage in active studying throughout the term, including:
- Weekly lecture summaries
- Rewriting notes/key points
- Flash cards/self testing and reflection
Find study partners

What is Genetics?

The study of genes, heredity, and how genetic variations affect living organisms

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Description

Explore the fascinating topics of cell division through mitosis, Mendel's Law of Equal Segregation, and the Chromosomal Theory of Inheritance. This quiz also delves into the nuances of sex linkage, examining how sex chromosomes influence genetic traits. Test your understanding of these essential genetic concepts!