Genetics Chapter on Chromosomes and Alleles

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson
Download our mobile app to listen on the go
Get App

Questions and Answers

What are genes located on chromosomes referred to as?

  • Gene loci (correct)
  • Chromosomal pairs
  • Gene pairs
  • Alleles

In diploid organisms, how are chromosomes organized?

  • Randomly assorted chromosomes
  • Single chromosomes without pairs
  • Chromosomes in a linear form
  • Homologous pairs of chromosomes (correct)

What are two alleles occupying the same locus but from different origins called?

  • Polyallelic pairs
  • Heterozygous alleles (correct)
  • Identical alleles
  • Homologous alleles

Which of the following statements is correct about alleles?

<p>They govern the same characteristics but not necessarily contain identical information. (A)</p> Signup and view all the answers

Which term describes alleles that govern the same type of characteristics?

<p>Allelic genes (B)</p> Signup and view all the answers

What is a key condition for gene and genotype frequencies to remain constant in a population?

<p>Migration, mutation, and selection must be absent. (B)</p> Signup and view all the answers

If a zygote has homologous chromosomes, what can be inferred about the alleles it carries?

<p>They consist of one allele from each parent. (A)</p> Signup and view all the answers

Which of the following alleles could govern fur color?

<p>Brown and Black (D)</p> Signup and view all the answers

What happens during Anaphase I of meiosis?

<p>Homologous chromosomes separate and are pulled to the cell poles. (C)</p> Signup and view all the answers

Which statement correctly describes Telophase I in meiosis?

<p>Nuclear envelopes reform, but there is no Interphase that follows. (A)</p> Signup and view all the answers

What is the significance of Metaphase II in meiosis?

<p>Haploid chromosomes orient on the metaphase plate. (A)</p> Signup and view all the answers

What occurs immediately after Telophase II?

<p>Cytokinesis follows with cell membrane formation. (D)</p> Signup and view all the answers

Which phase involves the tetrads orienting on the metaphase plate?

<p>Metaphase I (A)</p> Signup and view all the answers

What happens to the chromosomes during Telophase II?

<p>Chromosomes decondense to become chromatin fibers. (D)</p> Signup and view all the answers

During which meiotic division do centromeres NOT divide?

<p>Meiosis I (B)</p> Signup and view all the answers

What occurs in the prophase of Meiosis II?

<p>There is no prophase. (B)</p> Signup and view all the answers

What will be the outcome if a black heterozygote mouse is crossed with a homozygous recessive brown mouse?

<p>Offspring will be black heterozygous or brown homozygous in a 1:1 ratio. (A)</p> Signup and view all the answers

What is the primary purpose of performing a backcross?

<p>To test the genotype of an organism. (C)</p> Signup and view all the answers

Which of the following statements best describes Mendel's Second Law?

<p>Alleles of different genes assort independently of each other. (B)</p> Signup and view all the answers

What will be the phenotype of all offspring if a homozygous black mouse (BB) is crossed with a homozygous recessive brown mouse (bb)?

<p>All offspring will be black. (B)</p> Signup and view all the answers

In a cross between a black heterozygote mouse (Bb) and a homozygous recessive brown mouse (bb), which best describes the possible genotypes of the offspring?

<p>50% Bb and 50% bb. (B)</p> Signup and view all the answers

What is the genotypic ratio in the F2 generation resulting from a self-cross of the F1 generation?

<p>1 : 2 : 1 (A)</p> Signup and view all the answers

Which combination of alleles does the F1 generation consist of?

<p>Bb (A)</p> Signup and view all the answers

What phenotype ratio is expected in the F2 generation when crossing the F1 generation?

<p>3 : 1 (C)</p> Signup and view all the answers

What are the possible gametes produced by the F1 generation?

<p>B and b (D)</p> Signup and view all the answers

What does the term 'P1 generation' refer to?

<p>The first parental generation (B)</p> Signup and view all the answers

Which of the following best describes the F2 generation outcomes in terms of combinations?

<p>4 combinations possible (D)</p> Signup and view all the answers

In the F2 generation, what is the correct description of the allele dominance?

<p>B is dominant over b (C)</p> Signup and view all the answers

What is the significance of the Law of Segregation in relation to the offspring's genotypes?

<p>It states that alleles segregate during gamete formation. (A)</p> Signup and view all the answers

What is the frequency of the homozygous recessive genotype (aa) when the frequencies of alleles A and a are both 50%?

<p>0.25 (B)</p> Signup and view all the answers

How is the frequency of heterozygous individuals calculated from the allele frequencies?

<p>2pq (D)</p> Signup and view all the answers

In the context of population genetics, if $p + q = 1$, which statement is true about the population?

<p>All alleles in the population are represented. (B)</p> Signup and view all the answers

Given that 2 newborns of a population of 20,000 have Tay-Sachs disease, what is the value of q (frequency of allele a)?

<p>0.001 (B)</p> Signup and view all the answers

According to the Hardy-Weinberg principle, what equation represents the relationship of genotype frequencies in a population?

<p>p^2 + 2pq + q^2 = 1 (A)</p> Signup and view all the answers

If the carriers of Tay-Sachs disease are calculated to be 400 in a city of 20,000, what is the probability of an individual being a carrier?

<p>1/50 (B)</p> Signup and view all the answers

What is the probability of obtaining a homozygous dominant individual (AA) from two heterozygous parents (Aa)?

<p>0.25 (C)</p> Signup and view all the answers

In a population where the frequency of allele A is 0.99, what is the expected frequency of homozygous dominant individuals?

<p>0.9801 (A)</p> Signup and view all the answers

What is the expected genotype frequency for the homozygous dominant genotype (AA) in this population?

<p>0.49 (B)</p> Signup and view all the answers

How is the frequency of allele A calculated from the genotype frequencies?

<p>0.49 + 1/2(0.42) (A)</p> Signup and view all the answers

What does the Hardy-Weinberg Principle state regarding allele frequencies?

<p>They remain stable in succeeding generations. (D)</p> Signup and view all the answers

What is the expected frequency of homozygous recessive genotype (aa) in this population?

<p>0.09 (D)</p> Signup and view all the answers

Which formula is used to express genotype frequencies based on allele frequencies in a population?

<p>p^2 + 2pq + q^2 = 1 (B)</p> Signup and view all the answers

What does the term 'random mating' imply in the context of calculating genotype frequencies?

<p>There is no preference or bias in mate selection. (C)</p> Signup and view all the answers

How do heterozygous alleles contribute to calculating allele frequencies?

<p>Half of their frequency is added to each allele frequency. (B)</p> Signup and view all the answers

Which of the following statements best describes Mendel’s Law of Segregation?

<p>Organisms with two alleles for a trait will pass only one allele to their offspring. (D)</p> Signup and view all the answers

Flashcards

Crossing Over

Chromosomes pair up and exchange genetic material, increasing genetic diversity.

Meiosis I: Anaphase I

Homologous chromosomes separate, reducing the chromosome number by half.

Meiosis I: Prophase I

Chromosomes condense and become visible, forming tetrads.

Meiosis II: Anaphase II

Sister chromatids separate, leading to four haploid daughter cells.

Signup and view all the flashcards

Meiosis I: Metaphase I

Tetrads align on the equator of the cell, ready to separate.

Signup and view all the flashcards

Meiosis: Result

Haploid daughter cells with half the original chromosome number are formed.

Signup and view all the flashcards

Gametogenesis

The process that produces gametes (sex cells), like sperm and egg.

Signup and view all the flashcards

Meiosis II: Metaphase II

Sister chromatids align on the equator of the cell, about to separate.

Signup and view all the flashcards

Gene Loci

Specific locations on chromosomes where genes reside.

Signup and view all the flashcards

Homologous Chromosomes

Pairs of chromosomes that have the same genes in the same order, but may have different alleles - one from each parent.

Signup and view all the flashcards

Alleles

Alternative forms of a gene that occupy the same locus on homologous chromosomes.

Signup and view all the flashcards

Diploid

Having two sets of chromosomes, one from each parent.

Signup and view all the flashcards

Fertilization

The fusion of a sperm and an egg, resulting in a diploid zygote.

Signup and view all the flashcards

Meiosis

The process of cell division that reduces the chromosome number by half and produces four haploid gametes.

Signup and view all the flashcards

Genetics

The study of inheritance patterns, including how traits are passed from one generation to the next.

Signup and view all the flashcards

Hardy-Weinberg Principle

The Hardy-Weinberg equation shows how allele and genotype frequencies are related. It describes how these frequencies remain stable in large populations over generations.

Signup and view all the flashcards

Population Equation (p + q = 1)

The total frequency of all alleles for a specific trait in a population is always 1. For example, if we have two possible alleles for a trait, A and a, the frequency of A (p) plus the frequency of a (q) equals 1.

Signup and view all the flashcards

Hardy-Weinberg Equilibrium

The Hardy-Weinberg equation states that the frequencies of alleles and genotypes remain constant in a population over time. This applies to an ideal population where there are no evolutionary influences.

Signup and view all the flashcards

Punnett Square

A Punnett square visualizes the possible combinations of alleles from parents to predict the genotypes of offspring.

Signup and view all the flashcards

Genotype Frequencies in Hardy-Weinberg Equation

The Hardy-Weinberg equation helps us predict the frequencies of different genotypes in a population: p² represents the frequency of the homozygous dominant genotype, 2pq represents the frequency of the heterozygous genotype, and q² represents the frequency of the homozygous recessive genotype.

Signup and view all the flashcards

Tay-Sachs Disease

Tay-Sachs disease is a genetic disorder caused by a recessive allele. Individuals with two copies of the recessive allele (aa) develop the disorder.

Signup and view all the flashcards

Carriers (of a Recessive Trait)

Carriers of a recessive genetic disorder have one copy of the recessive allele (Aa) but do not express the disorder themselves. They can still pass the recessive allele to their offspring.

Signup and view all the flashcards

Calculating Carrier Frequency

The Hardy-Weinberg equation can be used to calculate the frequency of carriers for genetic disorders in a population. By knowing the frequency of the disease (q²) we can calculate the frequency of carriers (2pq).

Signup and view all the flashcards

Genotype Frequencies

Genotype frequencies refer to the proportion of individuals in a population carrying each possible genotype for a specific trait.

Signup and view all the flashcards

Hardy-Weinberg Equation

This equation (p² + 2pq + q² = 1) calculates the expected genotype frequencies based on allele frequencies.

Signup and view all the flashcards

Allele Frequency

The frequency of a specific allele in a population is calculated by considering the number of homozygous individuals plus half the number of heterozygous individuals.

Signup and view all the flashcards

Calculating allele 'A' frequency

The frequency of allele 'A' is calculated by adding the frequency of the homozygous dominant genotype (AA) to half the frequency of the heterozygous genotype (Aa).

Signup and view all the flashcards

Calculating allele 'a' frequency

The frequency of allele 'a' is calculated by adding the frequency of the homozygous recessive genotype (aa) to half the frequency of the heterozygous genotype (Aa).

Signup and view all the flashcards

Assumptions of Hardy-Weinberg

The Hardy-Weinberg Principle assumes that natural selection, genetic drift, mutation, migration, and non-random mating are not acting on the population.

Signup and view all the flashcards

F1 Generation

The first generation of offspring in a genetic cross, produced by crossing two parental individuals.

Signup and view all the flashcards

F2 Generation

The offspring produced from a self-cross of the F1 generation.

Signup and view all the flashcards

Law of Segregation

The principle that during gamete formation, each allele for a trait separates from its counterpart, so that each gamete carries only one allele.

Signup and view all the flashcards

Heterozygote

A heterozygote carries two different alleles for a trait (e.g., Bb).

Signup and view all the flashcards

Self-Cross

The offspring produced from a cross between individuals of the same generation or between individuals with the same genotype.

Signup and view all the flashcards

Phenotype

The observable physical or biochemical characteristics of an organism, resulting from the interaction of its genotype with the environment.

Signup and view all the flashcards

Genotype

An organism's genetic makeup, the combination of alleles it carries.

Signup and view all the flashcards

Backcross (Test Cross)

A cross between an individual with an unknown genotype and a homozygous recessive individual to determine the unknown genotype.

Signup and view all the flashcards

Homozygous

An individual with two identical alleles for a specific trait.

Signup and view all the flashcards

Study Notes

Genetics: Basic Principles of Heredity, Meiosis and Mendel's Principles

  • Genetics is the study of heredity, focusing on how characteristics are passed from parents to offspring.
  • The study of inheritance began in the 1850s.
  • The process of meiosis, a type of cell division, occurs during gametogenesis (the production of gametes, or sex cells). The process makes gametes with half the number of chromosomes compared to the parent cell.
  • Meiosis involves two rounds of cell division and results in four unique haploid cells. This process involves the exchange of genetic material between homologous chromosomes, creating new combinations.
  • The process of meiosis occurs in specialized reproductive structures (testes and ovaries) in animals to produce sperm and ova.
  • Meiosis involves complex steps:
    • Chromatids become replicate chromosomes.
    • Maternal and paternal homologues associate.
    • Formation of tetrads (homologous chromosomes pairing up).
    • Chromosome synapsis and crossing-over.
    • Alignment at metaphase plate and separation.
    • A second alignment and separation.
    • Production of four uniquely different cells.
  • Pre-meiotic interphase is similar to mitosis but with a longer S-phase where DNA and organelles duplicate, and ATP is stored for meiosis.
  • Prophase I has multiple stages:
    • Leptotene: Chromosomes become visible.
    • Zygotene: Homologous chromosomes begin to pair (synapse).
    • Pachytene: Chromosome pairing is complete; chromosomes coil around each other to form a bivalent.
    • Diplotene: The chromosomes visibly divide into two closely paired chromatids.
    • Diakinesis: Chromatids contract fully. The centrioles separate and move to opposite poles of the cell. The nucleoli disappear and the nuclear envelope breaks down.
  • Recombination occurs during crossing over at chiasmata, leading to genetic variation in offspring.
  • Metaphase I: Tetrads become oriented on the metaphase plate, with each chromosome on opposite sides of the equator.
  • Anaphase I: The attraction between homologous chromosomes lapses. Chromosomes separate to the poles of the cell.
  • Telophase I: A short telophase occurs at the end of the first meiotic division, with nuclear envelopes potentially reforming, followed by cytokinesis.
  • Metaphase II: Haploid chromosomes orientate on the metaphase plate.
  • Anaphase II: Centromeres divide and sister chromatids are separated to opposite poles of the cell.
  • Telophase II: Four nuclei are formed, each with half the original number of chromosomes. New nuclear envelopes form, and chromosomes become chromatin fibers again.
  • Cytokinesis follows.
  • Genetic Terminology:
    • Alleles: Different forms of a gene.
    • Locus/Loci: The specific location of a gene on a chromosome.
    • Wild type allele: The normal gene form.
    • Mutant allele: A dissimilar or abnormal gene form.
    • Dominant allele: An allele that masks the expression of a recessive allele.
    • Recessive allele: An allele that is masked by a dominant allele.
    • Phenotype: The observable physical traits of an individual (e.g., blonde hair, purple flowers).
    • Genotype: The genetic makeup of an individual (e.g., TT, Tt, tt).
    • Homozygous: Having two identical alleles for a gene (e.g., TT or tt).
    • Heterozygous: Having two different alleles for a gene (e.g., Tt).
  • Probability in Genetics:
    • In a large population, allele and genotype frequencies can remain constant without evolutionary forces.
    • Calculations of genotype frequencies can use allele frequencies in the population and the Punnett Square.

Mendel's Laws of Segregation and Independent Assortment

  • Inheritance of traits is governed by "segregation" of traits during gamete formation,
  • The first filial generation (F1) will always express the dominant phenotype when crossing true-breeding parents.
  • The second filial generation (F2) will show a 3:1 phenotypic ratio of the dominant to recessive trait.
  • Mendel's second law states independent assortment where each gene pair segregates independently during gamete formation. This leads to a variety of combinations in the offspring with a 9:3:3:1 ratio.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Genetics: The Basic Principles of Heredity, Meiosis, and Mendel's Principles PDF

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser