Ch. 10 Sexual Reproduction and Genetics

What is the chromosome number of daughter cells in Mitosis?

2n

What is the approximate number of human genes?

69,000 genes (1500 x 46)

Punnett Squares

A chart developed by Dr. Reginald Punnet in the early 1900's. It is used to predict probabilities of genetic outcomes if you know the genetic makeup of both parents. The squares represent all possible combinations of alleles in the children. It backed up Mendel's experiments. The larger the number of offspring, the more closely the results will match the ratio predicted by this square.

tetrad

A four-part structure that forms during the prophase of meiosis and consists of two homologous chromosomes, each composed of two sister chromatids.

genes

A segment of DNA on a chromosome that codes for a specific trait. There are about 1500 of these on each chromosome.

recessive gene

A trait having two different alleles for the same gene and is only seen in the offspring when there is no dominant allele present. It is hidden. It is represented by a lower case letter.

dominant gene

A trait that can be seen in the offspring whenever it is present . There can be 2 alleles the same or at least one allele that is inherited. It is represented by a capital letter.

polyploidy

An organism that has one or more extra sets of chromosomes as a result of an accident of cell division during meiosis

How is chromosome gene linkage an exception to the Law of Independent Assortment?

Genes that are linked together on a chromosome usually travel together during meiosis and do not randomly sort during chromosome lineup in Metaphase I (like sex cell and color blindness, and sex cell and baldness).

germ cells

Specialized cells in the reproductive organs where gametes of sperm and egg cells are produced where they ultimately undergo meiosis, thereby producing haploid gametes that transmit genes to the next generation.

law of segregation

The First law of heredity stating that pairs of alleles for a trait separate when gametes are formed and then unite during fertilization in different combinations.

What is Mendel's Third Law of genetics?

The Law of Dominance states that the dominant trait will show and the recessive traits will be masked unless there are two recessive traits paired up, then the recessive trait will become visible.

What is Mendel's Second Law of Genetics?

The Law of Independent Assortment states that a random distribution of alleles occurs during gamete formation causing genetic variation.

What is Mendel's First Law of Genetics?

The Law of Segregation states that the two alleles separate during meiosis causing genetic variation.

Law of independent assortment

The alleles of different genes separate independently and randomly of one another during gamete formation

the "P" generation

The original organisms of a mated pair or the parent generation

haploid

a cell that contains one copy of chromosomes or "n" number of chromosomes; in humans this number is 23

diploid

a cell that contains two copies of each chromosome or "2n" chromosomes

chromosome

a cellular structure that contains DNA

dihybird

a cross between organisms involving two pairs of contrasting traits and means "two" and its phenotype ratio is 9:3:3:1. They are from the F1 generation because they are heterozygous for both traits.

monohybrid

a cross between two organisms where only one trait is being studied and means "one" and its phenotype ratio is 3:1.

What is the product or end result in fertilization?

a diploid fertilized egg

In Meiosis II Metaphase II

a haploid number of chromosomes lines up near the center of the cell by the spindle fibers

synapsis

a process where homologous pairs find each other and loosely bond together to form a tetrad and are held together along their lengths by a protein that acts like a "zipper"

gamete

a sex cell that is a haploid cell and carries "n" number of chromosomes

heterozygous

an organism that has two different alleles for a given trait; one dominant and one recessive

homozygous

an organism that has two identical alleles for a given trait; it has either two dominant, or two recessive alleles.

hybrids

are heterozygous organisms; this happens when parents (the P generation) have different forms of a trait are crossed like one dominant and one recessive trait.

Why do plant cells not have centrioles?

because the shape of a plant cell is square or rectangular, naturally creating poles in the center of the cell.

In Meiosis I Cytokinesis I

cell divides into two cells and might go into interphase again but this time the DNA is not copied; meiosis is half finished here

In Meiosis II Cytokinesis II

cell divides or splits into 4 haploid cells with different genetic variations and each with "n"number of chromosomes for that species

In Meiosis II Prophase II

chromosomes condense and spindle apparatus forms

Name one thing that occurs in meiosis that causes genetic variations?

crossing over

What produces genetic variations?

diversity of allells by crossing over; random sorting of chromosomes during meiosis, and increases during fertilization by combining genetic material from two different individuals.

In Meiosis I Anaphase I

each homologous chromosome is guided by spindle fibers and move toward opposite poles of the cell, the number of chromosomes reduce from 2n to n.

How do protists and most plants reproduce?

either asexually or sexually

What is the number of daughter cells in Meiosis?

four

What is the product or end result in meiosis?

four haploid cells

Name another thing that occurs in meiosis that causes genetic variations?

genetic variation by random arrangement of chromosomes at the equator

In Meiosis I Prophase I

homologous chromosomes condense and form homologous pairs in a process called synapsis, where the pairs are held tightly together by a protein that acts like a zipper; crossing over occurs here; chromosomes begin to move to opposite sides

What happens in meiosis?

involves 2 cell divisions "I" that reduces the number of chromosomes by half thru separation of "homologous" chromosomes; each of the homologous chromosomes still have 2 sister chromatids and do not split; only takes place in the reproductive organs of plants and animals; gametes are formed here

allele

is a different form of a gene passed on from generation to generation like the different hair color gene ex: brown or blonde

genotype

is an organism's genes, or allele combinations (or allele pairs) represented by capital or lowercase letters

phenotype

is what an organism looks like or other detectable characteristics such as yellow or green colored peas, and round or wrinkled shaped peas.

What is one thing different in a pair of homologous chromosomes unlike a heterozygous pair?

it has an exact version of each gene on the homologous chromosomes (YY, or yy)

What is one of three characteristics of a pair of homologous chromosomes?

length of the homologous chromosomes

Kinetichores

microtubules that are connected to the centromere on the chromosome

What is the chromosome number of daughter cells in Meiosis?

n

What is the product or end result in crossing over?

new combinations of genetic material on chromosomes

Interphase I

occurs before meiosis begins, carries out metabolic processes, copies the DNA, and makes proteins

crossing over

occurs when sections of chromosomes change places with sections of its homologous chromosome, centrioles move to opposite poles, spindle fibers form and bind to sister chromatids at the centromere

What is the number of DNA replications in Meiosis?

one

What is the number of DNA replications in Mitosis?

one

What is the number of cell divisions in Mitosis?

one

How do mammals reproduce?

only sexually

homologous chromosomes

pairs of chromosomes (one from each parent) that carries the same traits or genes at the same place, are the same length, and centromeres are in the same spot.

What is one of three characteristics of a pair of homologous chromosomes?

position of the centromere on the homologous chromosomes

What is one of three characteristics of a pair of homologous chromosomes?

position of the genes on the homologous chromosomes

"n"

represents the number of chromosome pairs in an organism

What happens in crossing over?

segments of homologous chromosomes break and change places

protists

simple animals

In Meiosis I Metaphase I

spindle fiber attaches to kinetichores and pulls the pair of homologous chromosomes to the middle of the cell

What are examples of polyploidy?

strawberries, sugar cane, gold fish, wheat bread and coffee

Gregor Mendel

the Father of Genetics, an Austrian Monk, in the 1800's who experimented with pea plants and published his findings

In Meiosis II Telophase II

the chromosomes reach the poles, and the nucleus and nucleolus reforms within all 4 new haploid cells but have not split apart yet

In Meiosis I Telophase I

the homologous chromosomes reach opposite poles and contains only one member of a pair of homologous chromosomes; the nucleus and nucleolus begin to reappear; Sister chromatids might not be identical because of crossing over during synapsis in Prophase I

genetic recombination

the new combination of genes produced by crossing over and independent assortment

the "F2" generation

the offspring of the F1 generation

the "F1" generation

the offspring of the Parent generation

In Meiosis II Anaphase II

the sister chromatids are pulled apart at the kinetichores by the spindle fibers and sister chromatids are pulled to the opposite poles of the cell

genetics

the study or science of heredity

true breeding or blood-lines

these traits stayed the same from generation to generation

Name one of 3 things that leads to more genetic diversity during meiosis?

thru crossing over which make haploid daughter cells that are not identical resulting

Name one of 3 things that leads to more genetic diversity during meiosis?

thru fertilization when 2 haploid gametes combine

Name one of 3 things that leads to more genetic diversity during meiosis?

thru the law of independent arrangement where random arrangement of chromosomes line up at the equator

What is the purpose of meiosis?

to produce four different haploid daughter cells that cause genetic variations in species

What is the number of cell divisions in Meiosis?

two

What is the number of daughter cells in Mitosis?

two

What happens in fertilization?

two haploid gametes or sex cells, one from each parent combine, so now it has "2n" number of chromosomes.

asexual reproduction

when an organism inherits all of its chromosomes from one parent; it is genetically identical to its parent. A type of reproduction by budding or by the division of a single cell or the entire organism into two or more parts. There are no meiosis stages. Examples are bacteria, some plants, and some protists (simple animals).

sexual reproduction

when an organism inherits its homologous chromosomes from two different parents.Examples are some plants, some protist ( simple animals) and always complex animals.