Bio 101 Chapter 13

What is nondisjunction?

An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell

Compare and contrast mitosis with meiosis.

Both: types of cell division; produce daughter cells; have PMAT stages Differences: mitosis only has one round of cell division, meiosis has two; mitosis only occurs in somatic cells, while meiosis occurs in sex cells; mitosis produces daughter cells that are identical to the parent cell, while meiosis produces haploid cells that only have half of the normal number of chromosomes

How do crossing over, independent assortment, and random fertilization contribute to genetic diversity? Why is genetic diversity important in populations of organisms?

Crossing over produces recombinant chromosomes, which combine DNA inherited from each parent In independent assortment, each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs A human egg cell is fertilized randomly by one sperm, leading to genetic variety in the zygote. genetic diversity helps maintain the health of the environment

What accounts for the genetic similarity between daughter cells and parent cells in mitosis and the genetic dissimilarity between daughter cells and parent cells of meiosis?

Each daughter cell receives one duplicated chromosome from each pair.

Turner Syndrome

XO. female with single X chromosome

Poly-X females

XXX female with several x chromosomes

What are the four types of changes in chromosome structure that we discussed in class? (study slide 53).

deletion, duplication, translocation, and inversion

Sexual life cycles involve an alternation of diploid and haploid stages. Describe the human life cycle in terms of diploid and haploid stages.

humans are diploid organisms (46) with body cells containing two sets of chromosomes. humans have haploid gametes (23) that have only one member of each homologous pair of chromosomes.

How do the results of nondisjunction in meiosis I compare with the results of nondisjunction during meiosis II?

in meiosis I the homologous chromosome fail to separate producing all the gametes to be abnormal. on meiosis II the sister chromatids fail to separate producing 2 abnormal and two normal

Jacob's Syndrome

(XYY) - tall, persistent acne, speech and reading problems

Swyer Syndrome

XY female

Klinefelter syndrome

YXX. no matter how many X chromosomes are present, the presence of a chromosome Y renders the individual male with underdeveloped testes, prostate and breast development

What genetic disorder discussed in class is a type of trisomy? What genetic disorder discussed in class is a type of monosomy?

down syndrome is aka trisomy 21 Turner syndrome

Be able to describe and identify the various stages of meiosis I and II. NOTE: make sure that when you answer a question on the test about the stages of meiosis that you specify if each phase is in the first or second division (i.e Anaphase I vs Anaphase II).

meiosis I: chromosomes are replicated prior >prophase I: homologous chromosomes pair up and cross over and exchange genetic material between non sister chromatids >metaphase I: homologous pairs align themselves against each other side by side at the metaphase plate >anaphase I: the two members of a homologous pair separate >telophase I: each daughter cell receives one duplicated chromosome from each pair meiosis II: DNA is not replicated between meiosis I and II >prophase II: sister chromatids separate and move to opposite poles >metaphase II: the four daughter cells contain one daughter chromosome from each pair >anaphase II: each daughter chromosome consists of a single chromatid >telophase II: the daughter cells are haploid

When does mitosis occur in the human life cycle, when does meiosis occur (see Figure 13.5)?

mitosis occurs when the zygote produces somatic cells by mitosis and develops into an adult. meiosis occurs when producing gametes and result in one set of chromosomes in each gamete

What is the difference between monosomy and trisomy?

monosomy has only one particular type of chromosome while trisomy has three of a particular type of chromosome

Why is it necessary for there to be a reduction of chromosomes during meiosis for sexually reproducing organisms?

necessary in sexually reproducing organisms to maintain the species number of chromosomes. Gametes or sex cells must have half the chromosomes that the parent cell has.

Is it possible for a person who is biologically female to have a Y chromosome? Explain.

no because males have xy while female have xx provide their reproductive parts