Genetics, Mitosis and Meiosis

Biology 1- EOC Review

Genetics- Mendel’s Laws

- Law of Segregation- Two alleles will segregate from each

other so that each gamete carries only a single copy of each allele.

- Law of Independent Assortment - Genes of different traits can segregate

independently during gamete formation.

Dominant vs. Recessive

Dominant Trait is shown/seen Must have a CAPITAL letter to be

dominant Recessive

Trait is masked or not seen if dominant allele is present

Must have a lowercase letter

Incomplete Dominance

The heterozygous phenotype is a blend between the two homozygous phenotypes.

CRCR= Red flowers CRCW= Pink flowers CWCW= White

flowers

Codominance

Both alleles are expressed in the phenotype

Multiple Alleles and Polygenic Traits

Multiple Alleles Genes that have more than two alleles More than two possible alleles exists in a

population. Ex- coat color in rabbits (full color, chinchillas, Himalayan, and albino.

Polygenic Traits Traits that are produced by the interaction

of several genes. Show a wide range of traits. Ex- human skin

colors.

Cell Division

Somatic cells- a body cell that is not passed on to future generations.

Sex or germ cells- a cell that is destined to become a gamete (egg or sperm).

Diploid (2N) – a cell with 2 chromosome sets in each cell; somatic cells.

Haploid (N) – a cell with 1 chromosome set in each cell; germ cells.

Cell Cycle- Interphase

The cell cycle has two major stages; interphase and mitotic phase (M).

The longest phase of the cell cycle is interphase.

Consists of 3 stages; G1, S, and G2.

Interphase

G1 Stage where cells spend the most time. G- growth phase to prepare for S phase.

S S- synthesis Stage of DNA replication

G2 G- growth period. Prepares cell for mitosis.

Mitosis

Cells that undergo mitosis produce genetically identical cells (2N).

Four stages of mitosis Prophase Metaphase Anaphase Telophase/Cytokinesis

Prophase

Beginning of cellular division

Chromosomes condense

Centrioles migrate to poles

Nuclear envelope disappers.

Metaphase

Chromosomes line up along the equator

Centrioles are on opposite poles of the cell

Spindle fibers attach to the centromeres

Anaphase

The centromeres divide

Go from two sister chromatids to 2 separate chromosomes

Spindle fibers pull the chromosomes to opposite poles

Telophase/Cytokinesis

Telophase Chromosomes are at

poles Nuclear envelope

reforms Cytokinesis

Division of cytoplasm Cleavage furrow forms

to separate daughter cells

Cell plate forms in plant cells (eventually forms cell wall)

Meiosis

Meiosis occurs in sexual reproduction A diploid germ cell produces four haploid

daughter cells that become gametes. Have two major stages Meiosis I and

Meiosis II.

Meiosis I- Prophase I

Chromatids pair and crossing over occurs.

Chromosomes condense

Spindle fibers form Nuclear envelope

disappears

Meiosis I- Metaphase I

Chromatid pairs line up along the equator

Spindle fibers attach

Meiosis I- Anaphase I

Spindle fibers pull chromosomes to opposite poles

Sister chromatids remain attached

Meiosis I- Telophase I

Nuclear envelopes reassemble

Spindle fibers disappear

Cytokinesis divides cell.

Meiosis II- Prophase II

Nuclear envelopes disappears

Spindle fibers form

Meiosis II- Metaphase II

Chromosomes line up along the equator

Meiosis II- Anaphase II

Sister chromatids are separated

Spindle fibers pull the separate chromosomes to opposite poles

Meiosis II- Telophase II

Nuclear envelope forms

Spindle fibers disappear

Chromosomes unravel

Cytokinesis divides the cells

Have four haploid daughter cells

Mitosis vs. Meiosis

Mitosis Meiosis2 identical

daughter cells4 genetically

different daughter cells

Diploid (2N) diploid (2N)

Diploid (2N) haploid (N)

Asexual reproduction-

organisms reproduce by

mitosis

Sexual reproduction-

organism produce gametes

Review Questions

Mitosis and meiosis are processes involved in cellular reproduction. Which of the following describes an event that results from mitosis but NOT meiosis? a. Two stages of cell divisionb. Replication of cellular genetic materialc. Daughter cells that are identical to the

parent celld. Four daughter cells that are produced

from each parent cell

Review Questions

Mitosis and meiosis are processes involved in cellular reproduction. Which of the following describes an event that results from mitosis but NOT meiosis? a. Two stages of cell divisionb. Replication of cellular genetic materialc. Daughter cells that are identical to the

parent celld. Four daughter cells that are produced

from each parent cell

Review Questions

Which of the following best compares the processes of mitosis and meiosis? a. Mitosis involves one division cycle and results in diploid

daughter cells, while meiosis consists of two division cycles and results in haploid gametes

b. Mitosis involves one division cycle and results in haploid gametes, while meiosis consists of two division cycles and results in diploid daughter cells

c. Mitosis involves two division cycles and results in diploid daughter cells, while meiosis consists of one division cycle and results in haploid gametes.

d. Mitosis involves two division cycles and results in haploid gametes, while meiosis consists of one division cycle and results in diploid daughter cells.

Review Questions

Which of the following best compares the processes of mitosis and meiosis? a. Mitosis involves one division cycle and results in diploid

daughter cells, while meiosis consists of two division cycles and results in haploid gametes

b. Mitosis involves one division cycle and results in haploid gametes, while meiosis consists of two division cycles and results in diploid daughter cells

c. Mitosis involves two division cycles and results in diploid daughter cells, while meiosis consists of one division cycle and results in haploid gametes.

d. Mitosis involves two division cycles and results in haploid gametes, while meiosis consists of one division cycle and results in diploid daughter cells.

Review Questions

Which of the following best describes how the process of crossing over during meiosis leads to an increase in genetic diversity? a. During prophase I, DNA replication takes place, and

homologous chromosomes trade places with each other before lining up in preparation for metaphase

b. During prophase I, DNA segments are exchanged between homologous chromosomes, resulting in different combinations of alleles

c. During prophase II, fragments of DNA break off of chromosomes and attach to the ends of other chromosomes, resulting in different gene sequences

d. During prophase II, sister chromatids separate from each other, as they travel to opposite ends of the cell, DNA segments of nearby chromosomes are exchanged

Review Questions

Which of the following best describes how the process of crossing over during meiosis leads to an increase in genetic diversity? a. During prophase I, DNA replication takes place, and

homologous chromosomes trade places with each other before lining up in preparation for metaphase

b. During prophase I, DNA segments are exchanged between homologous chromosomes, resulting in different combinations of alleles

c. During prophase II, fragments of DNA break off of chromosomes and attach to the ends of other chromosomes, resulting in different gene sequences

d. During prophase II, sister chromatids separate from each other, as they travel to opposite ends of the cell, DNA segments of nearby chromosomes are exchanged

Review Questions

The allele for brown eyes is dominant to the allele for blue eyes. Which of the following best explains how two brown-eyed parents could produce a blue-eyed child? a. Each parent must be carrying the recessive

allele for blue eyesb. Eye color is a sex-linked trait and male children

could have only the allele for blue eyesc. Mutations after fertilization could alter gene

sequences and change allelesd. One parent must have had only blue eyed

parents

Review Questions

The allele for brown eyes is dominant to the allele for blue eyes. Which of the following best explains how two brown-eyed parents could produce a blue-eyed child? a. Each parent must be carrying the recessive

allele for blue eyesb. Eye color is a sex-linked trait and male children

could have only the allele for blue eyesc. Mutations after fertilization could alter gene

sequences and change allelesd. One parent must have had only blue eyed

parents

Review Questions

When an organism has more than 10 fingers or toes, the condition is known as polydactylism. Although polydactylism is rare, it is a dominant trait. If two cats that are heterozygous for polydactylism mate and have a litter with a total of 12 kittens, how many of them would you expect more than 10 fingers or toes? a. 0b. 6c. 9d. 12

Review Questions

When an organism has more than 10 fingers or toes, the condition is known as polydactylism. Although polydactylism is rare, it is a dominant trait. If two cats that are heterozygous for polydactylism mate and have a litter with a total of 12 kittens, how many of them would you expect more than 10 fingers or toes? a. 0b. 6c. 9d. 12

Review Questions

In pea plants, the allele for white flowers is recessive to the allele for purple flowers. In a generation of pea plants, 89 plants produced purple flowers and 31 plants produced white flowers. Which of the following is the best conclusion you can make about the parent plants of this generation? a. Both parent plants are heterozygous for flower colorb. Both parent plants were homozygous with purple flowersc. One parent plant had white flowers and the other was

heterozygous for flower colord. One parent plant was heterozygous for flower color, and

the other was homozygous with purple flowers

Review Questions

In pea plants, the allele for white flowers is recessive to the allele for purple flowers. In a generation of pea plants, 89 plants produced purple flowers and 31 plants produced white flowers. Which of the following is the best conclusion you can make about the parent plants of this generation? a. Both parent plants are heterozygous for flower colorb. Both parent plants were homozygous with purple flowersc. One parent plant had white flowers and the other was

heterozygous for flower colord. One parent plant was heterozygous for flower color, and

the other was homozygous with purple flowers

Review Questions

Meiosis allows a plant to produce offspring plants with which characteristic? a. A high rate of random mutationsb. Unique combinations of genetic materialc. Traits identical to those of the parent

plantd. Characteristics adaptive to the plants

environment

Review Questions

Meiosis allows a plant to produce offspring plants with which characteristic? a. A high rate of random mutationsb. Unique combinations of genetic materialc. Traits identical to those of the parent

plantd. Characteristics adaptive to the plants

environment

Review Questions

Suppose you cross two heterozygous tall pea plants, both with genotype Tt. What is the probability that the offspring will display the dominant trait?a. 100%b. 75%c. 50%d. 25%

Review Questions

Suppose you cross two heterozygous tall pea plants, both with genotype Tt. What is the probability that the offspring will display the dominant trait?a. 100%b. 75%c. 50%d. 25%

Review Questions

In biology, several different processes make up the cycles for cell division. In which complete process are four new cells created from one original cell? a. Anaphaseb. Meiosisc. Mitosisd. telophase

Review Questions

In biology, several different processes make up the cycles for cell division. In which complete process are four new cells created from one original cell? a. Anaphaseb. Meiosisc. Mitosisd. telophase

Review Questions

The process by which cells replicate is very different than the process by which gametes are produced. Which of the following do both processes have in common? a. Cytokinesisb. Haploid cells formc. Crossing-over occursd. Homologous chromosomes pair up

Review Questions

The process by which cells replicate is very different than the process by which gametes are produced. Which of the following do both processes have in common? a. Cytokinesisb. Haploid cells formc. Crossing-over occursd. Homologous chromosomes pair up