Meiosis

Haploid, diploid Monoploid, biploid Monosomic, disomic Asexual, sexual Gametes are ____, meaning that they carry one of each type of chromosome, while zygotes formed by fertilization are ______ containing two of each type of chromosome. Haploid, diploid Monoploid, biploid Monosomic, disomic Asexual, sexual 8

If an organism contains 20 chromosomes in each body (somatic) cell, then its gametes each contain __ chromosomes. 10 20 5 15 1

Which figure shows mitosis? The figure on the left The figure on the right Neither both 9

Meiosis, mitosis Mitosis, meiosis 9 _________ is used to produce new cells for growth and repair or for generation of clones of an organism during asexual reproduction. _______ is used to generate gametes for use in sexual reproduction. Meiosis, mitosis Mitosis, meiosis 9

II. What is meiosis? Meiosis is a process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid (2n) cell. This will form 4 genetically different sex cells (gametes) that are haploid (n). This means that it increases the differences between people’s DNA so that every person is genetically different.

II. What is meiosis? 23 23 23

III. Why does meiosis happen? Meiosis happens so that sperm and egg cells can be produced so that sexual reproduction can occur. Sexual reproduction is when two organisms combine their genetic information to produce genetically different offspring (babies).

Karyotype Picture that shows all the chromosomes in a body cell= of an organism = 23 pairs of homologous chromosomes used to diagnose chromosomal disorders (ex: Trisomy 21-Down Syndrome)

VI. What Happens During Meiosis? Before meiosis, our sex cells go through interphase, where the DNA replicates and the cell grows. DNA replication only occurs once in meiosis, but there are two divisions!!! (Meiosis I and Meiosis II)

VI. What happens during meiosis? Meiosis I: There are four parts of Meiosis I; Prophase I, Metaphase I, Anaphase I and Telophase I.

VI. What happens during meiosis?

VI. What happens during meiosis? The most important part of Meiosis I is Prophase I. During Prophase crossing over occurs. Crossing over is when parts of a chromosome exchange with another chromosome. This occurs within each homologous pair of chromosomes. This is important because it increases genetic variation.

Independent Assortment Independent Assortment occurs during metaphase I. Creates genetic variation between gametes Homologous pairs of chromosomes line up in the middle of the cell in a random order each time.

VI. What happens during meiosis? Meiosis II: There are four parts of Meiosis II; Prophase II, Metaphase II, Anaphase II and Telophase II.

VI. What happens during meiosis? At the end of Meiosis II, cytokinesis occurs. Meiosis II resembles Mitosis. The end result of the entire process of Meiosis (all 8 steps) is four haploid cells that are genetically different. .

Mitosis vs. Meiosis Mitosis Meiosis 1 division daughter cells genetically identical to parent cell produces 2 cells 2n  2n produces cells for growth & repair Meiosis 2 divisions daughter cells genetically different from parent produces 4 cells 2n  1n produces gametes

Non-disjunction- chromosomes do not separate properly during meiosis

Trisomy 21 : Down Syndrome Delayed mental and social skills Decreased muscle tone at birth Asymmetrical or odd-shaped skull Small skull Small mouth with protruding tongue Broad short hands Increased risk of developing Leukemia and Alzheimer’s later in life

Trisomy 18 : Edward’s Syndrome Most children die in the first year of life, some have lived 10 years Growth deficiency Feeding difficulties Breathing difficulties Developmental delays Mental Retardation Overlapped, flexed fingers Webbing of the second and third toes Clubfeet Structural heart defects at birth

Mitosis vs. Meiosis

Mitosis vs. Meiosis Mitosis Meiosis 1 division daughter cells genetically identical to parent cell produces 2 cells 2n  2n produces cells for growth & repair Meiosis 2 divisions daughter cells genetically different from parent produces 4 cells 2n  1n produces gametes

Mitosis Asexual Reproduction Fusion Meiosis Cell A has 4 chromosomes and Cell D has 2 chromosomes. What process created Cell D? Mitosis Asexual Reproduction Fusion Meiosis Cell A Cell B Cell C Cell D 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 10

Cell A is considered _______ while Cell D is considered ________. Haploid; Diploid Tetrad; Diploid Diploid; Haploid Homologous; Haploid Cell A Cell B Cell C Cell D 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Which of the numbers below best represents a chromatid? 1 2 3 4 Cell A Cell B 1 2 3 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 10

Which of the numbers below best represents homologous chromosomes? 1 2 3 4 Cell A Cell B 1 2 3 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 10

How can we best describe the diagram below? Two sister chromatids Homologous chromosomes One replicated chromosome Haploid chromsomes 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 10

What process is best demonstrated by the diagram below? Anaphase I Segregation of alleles Crossing over Independent assortment 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 10

Which of the following leads to genetic variation during meiosis? Crossing Over DNA replication Independent assortment Mitotic spindle formation All of the above (A, B, C, D) A & B A & D A, B, & D A & C 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 10

Which of the chromosomes below are homologous to chromosome number one? A and B B and C B C B and D Blonde hair Brown hair Blue Eyes A C D B ONE 10

Model Meiosis with Pop Beads!! Diploid = 4 chromosomes (2 homolgous pairs) Haploid = 2 chromosomes Gametes should be genetically different due to crossing over and independent assortment.