Chapter 11 Biology Meiosis and Sexual Reproduction

Asexual reproduction

Single individual passes all of its genes to its offspring without the fusion of gametes

For asexual reproduction reproduction usually goes through

Mitosis

Clone

Individual or group with genetically identical individuals from the same parent

Sexual reproduction combines cells from 2 parents through

Fertilization

In sexual reproduction, the parent cells are

Diploid, which contains 2 sets of chromosomes, one set inherited from each parent

Gametes are

Haploid which means they contain one set of chromosomes

Somatic cells are

Diploid

There are 46 somatic chromosomes in a human. T/F

T

Humans have a set of 26 gametes. T/F

False they have a set of 23 gametes

Homologous Chromosomes (homologs)

The 2 chromosomes in each pair

Homologs have identical

Length

Centromere position

staining pattern

Genes

Sex Chromosomes

Determine the sex of the individual

Females have what pair of chromosomes

XX

Males have what pair of chromosomes

XY

Autosomes

Chromosomes not directly involved in determining sex

Are autosomes the remaining 22 pairs of chromosomes in humans

Si

Meiosis

Reduces the number of chromosomes sets from diploid to haploid

Meiosis begins by the replication of chromosomes during

Interphase

Meiosis occurs in which 4 phases

Prophase I

Metaphase I

Anaphase I

Telophase I and Cytokenesis

Prophase I

Centrosomes move toward opposite poles

Chromatid condenses into chromosomes

Meiotic Spindle forms

What are sister chromatids held together by in prophase I

Cohesins

How does prophase I in meiosis differ from mitosis

Homologous chromosomes form and pair with a synapse

There is a crossing over which is the reciprocal exchange of genetic materials between nonsister chromatids

Chiasmata are the sites of crossover

How do sister chromatids and homologous chromosomes differ

Homologous are pairs of chromosomes in all cells except gametes

Homologous are inherited from mother and father

Homologous differ genetically

Homologous is held together synaptically

Sister chromatids are 2 copies of a single chromosome

Sister chromatids are formed during DNA replication

Sister chromatids are genetically identical

Sister chromatids are held together at synapses

Metaphase I

Pairs of homologs line up at the metaphase plate with one chromosome facing each pole

Chromosomes line up independently of how they were inherited (independent assortment)

Anaphase I

Microtubules pull homologous chromosomes apart

One chromosome of each pair moves toward opposite poles

Sister chromatids remain attached at the centromere

Telophase I

In the beginning each half of the cell has a haploid set of duplicated chromosomes

Each Chromosome still consist of 2 sister chromatids held together at their centromeres

Nuclear envelope forms

Cytokinesis

Occurs simultaneously, forming 2 haploid cells

In animal cells a cleavage furrow forms

In plant cells a cell wall forms

Meiosis II

Centrosomes are duplicated during this time

Prophase II

New spindle apparatus forms and connects to the kinetochores in each daughter cells

Chromosomes still consist of 2 chromatids

Nuclear envelope starts to fragment

Prometaphase

Spindle microtubules attach at kinetochores on each sister chromatid

Nuclear envelope disappears

Metaphase II

Sister chromatids line up at metaphase plate

2 sister chromatids of each chromosome are not identical

Anaphase II

Sister chromatids are pulled apart as kinetochore microtubules shorten

Sisters move toward opposite poles

Non-kinetochore microtubules lengthen, elongating the cells

Telophase II

Chromosomes arrive at opposite poles

Nuclei Form

Chromosomes begin decondensing into chromatin 

Cytokinesis II

Anima cells, cleavage furrow forms

Plant cells cell plate forms

Results in 4 haploid daughter cells

Each daughter cell is genetically distinct

Life cycle

Generation to generation sequence of stages in the reproductive history of organisms

Diploid-Dominant Life Cycle

In animals, multicellular individuals are diploids 

Haploid gametes are produced by meiosis

Fertilization of gametes fuse to form a zygote

Haploid dominant life cycle

Most fungi and some protists are multicellular individuals are haploid only

In plants and some algae there is both

Diploid and haploid multicellular stage

What makes haploid spores by meiosis

Sporophyte

Each spore grows by mitosis into a haploid individual called a what?

Gametotype