HMB265H1 Lecture Notes - Lecture 7: Walter Sutton, Homologous Chromosome, Allosome

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emeraldcrow840

20 May 2018

School

UTSG

Department

Human Biology

Course

HMB265H1

Professor

Maria Papaconstantinou

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Lecture 7: Meiosis and the Chromosomal Theory of Inheritance

Analysis of Chromosomes

• Walter Sutton – Studied great lubber grasshopper

• Body cells contained 22 chromosomes + X & Y chromosomes

• Gametes contained 11 chromosomes and X or Y in equal numbers

o After fertilization

▪ Females were XX

▪ Males were XY

• Homologous chromosomes are the same size and have similar banding

patterns, they also carry the same genes

• Metaphase chromosomes are classified by the position of the centromere

o Centromere near the middle→ Metacentric

o Centromere near the end→ Acrocentric

• Microscopy provided a means to follow movement of chromosomes

during cell division

o Mitosis: two daughter cells (somatic cells) contain same number

of chromosomes as parent cell

o Meiosis: daughter cells (sperm and egg) contained half the

number of chromosomes as the parents

• Gamete contains ½ the number of chromosomes as the zygote

• Haploid: cells that carry only a single chromosome set

• Diploid: cells that carry two matching chromosome sets

• n: the number of chromosomes in a haploid cell

• 2n: the number of chromosomes in a diploid cell

Meiosis produces haploid gametes

• Somatic Cells: divide mitotically and make up cast majority of organism’s tissues

• Germ Cells: specialized role in the production of gametes

o Arise during embryonic development in animals and floral development in plants

o Undergo meiosis to produce haploid gametes

o Gametes unite with gamete from opposite sex to produce diploid offspring

Karyotype

• Karyotypes can be produced by cutting micrograph images of stained chromosomes and arranging them in

matched pairs

o The sex chromosomes and autosomes are arranged in homologous pairs of

decreasing size

• Autosomes- pairs of non sex chromosomes arranged in homologous pairs

• Sex chromosome

o Provides bassi for sex determination

o One sex has matching pair

o Other sex has non-matching sex chromosomes

o Variation in sex determination between species

Chromosome

Female

Male

Organism

XX-XY

Mammals, Drosophila

XX-XO

Some grasshoppers

ZZ_ZW

Fish, Birds, Moths

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HMB265H1 Full Course Notes

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Document Summary

Lecture 7: meiosis and the chromosomal theory of inheritance. Chromosome theory correlates with mendel"s laws of inheritance. Each cell contains 2 copies of each chromosome. Chromosome complements appear unchanged during transmission from parent to offspring. Each cell contains 2 copies of each gene. Genes appear unchanged during transmission from parent to offspring. Alternative alleles segregate to different gametes to different gametes. Alternative alleles of unrelated genes assort pairs separate without regard to the assortment of other homologous chromosome pairs. At fertilization an egg"s set of chromosomes unite randomly with encountered sperm"s chromosomes. In all cells derived from a fertilized egg, chromosomes are of maternal origin, and other is paternal independently. Alleles obtained from one parent unite at random with those of another parent. In all cells derived from a fertilized gamete, of genes are maternal, and are paternal. X-linkage using drosophila: observed true-breeding sex ratios, observed sex:trait ratios.

Related Questions

M2A1 Worksheet: Mitosis and Meiosis

A dog is a diploid organisms and has 39 pairs of chromosomes (2n = 78), where n = 39 chromosomes from each parent. Use this example to answer the following question regarding chromosomal number.

INTERPHASE

How many chromosomes are present in the somatic cell?

What do they look like?

What are they âdoingâ in G1 of this phase?

What is happening in the S phase?

What is happening in the G2 phase?

What follows G2 phase in a somatic cell?

What follows G2 phase in a gamete cell?

MITOSIS

Number of chromosomes in the parent cell.

Number of chromatids in the parent cell.

Number of chromosomes in the daughter cell.

Number of chromatids in the daughter cell.

How many daughter cells are produced?

Are the daughter cells haploid or diploid?

How many cell divisions take place?

In what type of cell does this division occur?

Meiosis 1:

Number of chromosomes in the parent cell.

Number of chromatids in the parent cell.

Number of chromosomes in each Meiosis I daughter cell.

Number of chromatids in each Meiosis I daughter cell.

Are the daughter cells haploid or diploid at the end of Meiosis 1?

Meiosis II:

Number of chromosomes in the âparentâ cell (which is a daughter cell from Meiosis I).

Number of chromatids in the âparentâ cell.

Number of chromosomes in each Meiosis II daughter cell.

Number of chromatids in each Meiosis II daughter cell.

Are the daughter cells haploid or diploid at the end of Meiosis II?

Which phase or phases of Meiosis account for the genetic variability among the daughter cells? Howâ¦ what happens in this phase to create the diversity?

Comparing Mitosis and Meiosisâ¦..

How many daughter cells result from Mitosis? Are they diploid or haploid?

How many daughter cells result from Meiosis? Are they diploid or Haploid?

Cell structures and function: Match each organelle to its function:

Organelle Function

Lysosome 1. Lipid synthesis

Rough ER 2. Houses DNA

Nucleus 3. Energy extraction

Smooth ER 4. Dismantles debris

Golgi apparatus 5. detoxification

Mitochondria 6. Protein synthesis

Peroxisome 7. Processes secretions

What is the function of checkpoint proteins in the cell cycle?

How can all of a personâs cells contain exactly the same genetic material, yet specialize as bone cells, nerve cells, muscle cells and connective tissues?

What are the 3 primary germ layers?

Briefly, in one or two sentences, distinguish between

a bacterial cell and a eukaryotic cell

interphase and mitosis

mitosis and apoptosis

an autosome and a sex chromosome

homologous pair of chromosomes and a sister chromatid

centromere and centriole

chromosome and chromatid

monozygotic and dizygotic twins

allele and gene

-Complete the following sentences: metaphase of mitosis, prophase II of meiosis, crossing over, anaphase I of meiosis, variable, random fertilization, identical, random orientation, metaphase I of meiosis, prophase I of meiosis, metaphase II of meiosis, reduction division

Two processes that occur during meiosis produce genetically ____________ cells.

In a process called ____________ , paired homologous chromosomes align randomly at the cell equator. This occurs during this stage of cell division: ____________ .

In a process called ____________ , genetic material is exchanged between homologous chromosomes. This occurs during this stage of cell division: ____________ .

-Complete the following paragraph to describe nondisjunction and the resulting effects on chromosome number.

words: euploidy, primary nondisjunction, nomal, nondisjunction, secondary nondisjunction, homologous chromosomes, abnormal, trisomy, monosomy, sister chromatids, aneuploid

1.During meiosis I, ____________ separate and move towards opposite ends of the poles.

2.During meiosis II, ____________ separate and move towards opposite ends of the poles.

3.During meiosis I, if both members of a homologous pair go into the same daughter cell, ____________ is said to occur and no normal gametes are produced.

4.During meiosis II, if the sister chromatids fail to separate and both daughter chromosomes go into the same gamete, ____________ is said to occur. Half the gametes are aneuploid while the other half are euploid.

5.If an egg that contains 24 chromosomes instead of 23 chromosomes is fertilized by a normal sperm, ____________ is said to have occurred.

6.If an egg that contains 22 chromosomes instead of 23 chromosomes is fertilized by a normal sperm, ____________ is said to have occurred.

Title: Meiosis Lab

Part 1: Modeling Meiosis Without Crossing Over (reformat as needed)

Take photos of the following stages of your meiosis bead simulation. Insert and label the following images:

Meiosis 1: Prophase I and Metaphase I

Meiosis 2: Metaphase II and Telophase II

Part 2: Modeling Meiosis With Crossing Over (reformat as needed)

Take photos of the following stages of your meiosis bead simulation. Insert and label the following images:

Meiosis with Crossing Over: Metaphase I and Telophase II

Questions â use the lab Introduction, your textbook and other sources to answer the following.

What is the state of DNA at the end of meiosis I? Are the chromosomes replicated or unreplicated? Diploid or haploid?

Why are chromosomes important?

How are Meiosis I and Meiosis II different?

Name two ways meiosis contribute to genetic recombination or genetic variety.

Why do you use non-sister chromatids to demonstrate crossing over? What would happen if you crossed over sister chromatids?

How many chromosomes were present in your simulation when meiosis I started?

Why is it necessary to reduce the chromosome number in gametes, but not in other cells of an organism?

If humans have 46 chromosomes in each of their body cells, determine how many chromosomes you would expect to find in the following:

Sperm	Egg	Daughter cell after mitosis	Daughter cell after meiosis

Investigate a disease that is caused by a chromosomal mutation due to nondisjunction. When does the mutation occur? What chromosome is affected? What are the consequences?

HMB265H1 Lecture Notes - Lecture 7: Walter Sutton, Homologous Chromosome, Allosome

HMB265H1 Full Course Notes

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