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Reproduction

Producing offspring (e.g., in unicellular organisms like bacteria).

Growth

Increasing the size of multicellular organisms by increasing the number of cells.

Repair

Replacing damaged or dead cells in tissues.

Cell Renewal

Constantly producing new cells, such as in the skin, blood, and other tissues.

Binary Fission Steps

1. DNA Replication: The single DNA molecule in the cell is copied. 2. Chromosome Segregation: The two DNA copies move to opposite ends of the cell. 3. Cell Elongation: The cell stretches out as the two chromosomes are pulled apart. 4. Septum Formation: A new membrane (septum) forms at the center of the cell. 5. Cell Division: The cell divides into two separate daughter cells.

Organisms undergoing Binary Fission

Prokaryotic organisms like bacteria and archaea.

Reproduction Type of Binary Fission

Binary fission is asexual reproduction, as it does not involve the fusion of gametes.

Chromatin

The uncoiled, thread-like form of DNA found in a non-dividing cell.

Chromosomes

The condensed, tightly coiled form of DNA found in a dividing cell.

Diploid

A cell that has two sets of chromosomes (one from each parent). In humans, this number is 46 (23 pairs).

Haploid

A cell that has one set of chromosomes. In humans, this number is 23 (found in gametes, like sperm and eggs).

Sister Chromatids

Two identical copies of a chromosome, joined together by a centromere, that are created during DNA replication in preparation for cell division.

Centromere

The region of a chromosome where the two sister chromatids are joined together. It is also the attachment site for spindle fibers during cell division.

G1 Phase

The cell grows and performs normal functions.

S Phase

DNA replication occurs, doubling the DNA content.

G2 Phase

The cell continues to grow and prepares for division.

M Phase

The cell undergoes mitosis and divides into two daughter cells.

Cancer

Cancer results from mutations or disruptions in the cell cycle, leading to uncontrolled cell division.

Daughter Cells from Mitosis

Mitosis results in 2 daughter cells, each with the same chromosome number as the parent cell. In humans, this is 46 chromosomes (diploid).

Genetic Identity of Daughter Cells

The daughter cells are genetically identical to the mother cell (unless mutations occur).

Prophase

Chromosomes condense and become visible, and the nuclear membrane begins to break down. The spindle apparatus begins to form.

Metaphase

Chromosomes align at the cell's equator (metaphase plate).

Anaphase

Sister chromatids are pulled apart toward opposite poles of the cell.

Telophase

The chromatids reach the poles, and new nuclear membranes form around the separated sets of chromosomes.

Mitosis in Plant Cells

In plant cells, a cell plate forms during cytokinesis to divide the cytoplasm.

Mitosis in Animal Cells

In animal cells, a cleavage furrow forms to pinch the cell into two.

Cytoplasm Contents of Daughter Cells

Are the cytoplasm contents of daughter cells identical?

Cytoplasm

Contents of the daughter cells that are typically identical, though there may be slight variations due to the random distribution of organelles.

Interphase

The phase of the cell cycle when the cell is not dividing, consisting of the G1, S, and G2 phases, and is a time for growth, DNA replication, and preparation for cell division.

Meiosis

A type of cell division that reduces the chromosome number by half, resulting in the formation of gametes (sperm and egg cells), involving two rounds of division: meiosis I and meiosis II.

Nuclear divisions in meiosis

Two nuclear divisions occur in meiosis (meiosis I and meiosis II), resulting in four daughter cells.

Gametes

Reproductive cells (sperm and eggs) that carry half the genetic information of an organism (haploid).

Homologous chromosomes

Chromosome pairs, one inherited from each parent, that are similar in shape, size, and genetic content.

Bivalent pair

Two homologous chromosomes paired together during meiosis.

Tetrad

A structure consisting of four chromatids (two chromosomes, each with two chromatids) that form during meiosis I.

Prophase I

The stage in meiosis I where homologous chromosomes pair up and undergo crossing over.

Metaphase I

The stage in meiosis I where homologous chromosome pairs align at the metaphase plate.

Anaphase I

The stage in meiosis I where homologous chromosomes are pulled to opposite poles.

Telophase I

The stage in meiosis I where two haploid cells form, each with half the number of chromosomes.

Prophase II

The stage in meiosis II where chromosomes condense in each haploid cell.

Metaphase II

The stage in meiosis II where chromosomes align at the metaphase plate in each cell.

Anaphase II

The stage in meiosis II where sister chromatids are pulled apart.

Telophase II

The stage in meiosis II where four haploid daughter cells are formed.

Tetrad formation

Occurs during prophase I of meiosis when homologous chromosomes pair closely together and may exchange genetic material through crossing over.

Metaphase plate in metaphase I

Homologous chromosome pairs align at the metaphase plate.

Anaphase I separation

During anaphase I, the homologous chromosomes (not the sister chromatids) are separated and pulled to opposite poles.

Telophase I chromosome number

In telophase I, the chromosomes are haploid (half the original chromosome number) and still consist of two chromatids each.

Meiosis II vs Mitosis

Meiosis II is similar to mitosis in that it involves the separation of sister chromatids to produce daughter cells, but occurs in haploid cells, resulting in four non-identical haploid cells, while mitosis results in two identical diploid cells.

Genetic identity of daughter cells

The daughter cells in meiosis are not genetically identical to the mother cell or to each other due to genetic recombination and independent assortment.

Spermatogenesis

The process where diploid spermatogonia undergo meiosis to produce four haploid sperm cells, occurring in the testes.

Oogenesis

The process occurring in the ovaries that produces egg cells.

Oogenesis

The process where diploid oogonia undergo meiosis to produce one haploid egg and three polar bodies (which are non-functional).

Importance of Meiosis

Meiosis ensures genetic diversity and maintains the chromosome number across generations.

Genetic Variability in Meiosis

Meiosis promotes genetic variability through crossing over (exchange of genetic material between homologous chromosomes) and independent assortment (random distribution of chromosomes into gametes).

Chromosome Theory of Inheritance

The chromosome theory of inheritance states that genes are located on chromosomes, and it is these chromosomes that are inherited during reproduction.

Karyotype

A karyotype is the complete set of chromosomes in an organism, typically displayed in pairs according to size, shape, and number.

Autosome

An autosome is any chromosome that is not a sex chromosome. Humans have 22 pairs of autosomes.

Types of Sex Chromosomes

The two types of sex chromosomes are X and Y.

Male Sex Chromosomes

A male has one X and one Y chromosome (XY).

Female Sex Chromosomes

A female has two X chromosomes (XX).

Mutation

A mutation is a change in the DNA sequence, which can result in a change in the protein that is produced.

Types of Chromosome Mutation

The two types of chromosome mutations are structural mutations (involving changes to the chromosome structure) and numerical mutations (involving changes in the chromosome number).

Monosomy

Monosomy is when an individual has one copy of a chromosome instead of two (e.g., Turner syndrome, where there is only one X chromosome).

Trisomy

Trisomy is when an individual has three copies of a chromosome instead of two (e.g., Down syndrome, where there are three copies of chromosome 21).

Causes of Monosomy or Trisomy

A monosomy or trisomy is caused by nondisjunction, an error in meiosis where chromosomes fail to separate properly.

Common Autosomal Chromosome Abnormality

The most common autosomal chromosome abnormality is Down syndrome (trisomy 21).

Effects of Down Syndrome

A child with Down syndrome typically has intellectual disabilities, characteristic physical features, and an increased risk of certain health issues such as heart defects.

Risk Factors for Down Syndrome

Advanced maternal age (over 35 years old) is a significant risk factor for Down syndrome.

Turner Syndrome

Turner syndrome: One X chromosome (45,X). Symptoms include short stature, infertility, and heart defects.

Metafemale

Metafemale: Extra X chromosomes (e.g., 47,XXX). Symptoms include developmental delays or learning disabilities.

Klinefelter's Syndrome

Klinefelter's syndrome: One extra X chromosome in males (47,XXY). Symptoms include reduced fertility, breast development, and cognitive challenges.

Jacob's Syndrome

Jacob's syndrome: One extra Y chromosome in males (47,XYY). Symptoms may include tall stature and learning disabilities.

Causes of Structural Chromosome Changes

Most structural chromosome changes are caused by DNA breaks and errors in repair mechanisms during DNA replication.

Inversion

An inversion is a chromosomal mutation where a section of a chromosome breaks off, flips around, and reattaches.

Translocation

A translocation occurs when a piece of one chromosome breaks off and attaches to another chromosome.

Deletion

A deletion is a chromosomal mutation where a segment of a chromosome is lost.

Duplication

A duplication is a chromosomal mutation where a segment of a chromosome is copied and inserted into the chromosome again.

Blending Theory of Inheritance

States that offspring are a 'blend' or mixture of the traits of their parents.

Gregor Mendel

An Austrian monk and scientist who worked with pea plants in the 1850s and 1860s.

Mendel's First Law (Law of Segregation)

Each individual has two alleles for a gene, which segregate during gamete formation.

Mendel's Second Law (Law of Independent Assortment)

Genes for different traits are inherited independently of each other during gamete formation.

Alleles

Different versions or forms of a gene that arise by mutation and are found at the same place on a chromosome.

Dominant allele

An allele that expresses its trait even if only one copy is present (e.g., 'T' for tall plants).

Recessive allele

An allele that only expresses its trait when two copies of the recessive allele are present (e.g., 't' for short plants).

Gene locus

The specific location or position of a gene on a chromosome.

Homozygous

Having two identical alleles for a particular gene, either both dominant (e.g., 'TT') or both recessive (e.g., 'tt').

Heterozygous

Having two different alleles for a particular gene, one dominant and one recessive (e.g., 'Tt').

Genotype

The genetic makeup of an organism, representing the alleles it carries for a particular trait (e.g., 'Tt').

Phenotype

The observable physical or behavioral characteristics of an organism that result from its genotype (e.g., tall or short plant).

Punnett square

A diagram used to predict the genotypes and phenotypes of offspring from a genetic cross.

Testcross

Performed to determine the genotype of an individual exhibiting a dominant phenotype.

Phenotype ratio of offspring (homozygous dominant testcross)

If a test cross is performed with a homozygous dominant (e.g., 'AA') and a homozygous recessive (e.g., 'aa'), all offspring will show the dominant phenotype (100% dominant phenotype).

Phenotype ratio of offspring (heterozygote testcross)

If a test cross is performed with a heterozygote (e.g., 'Aa') and a homozygous recessive (e.g., 'aa'), the offspring will have a 1:1 ratio of dominant to recessive phenotypes.

Probability of independent events

Calculated by multiplying the probabilities of each event happening individually.

Monohybrid cross

Involves one trait (e.g., Tt x Tt).

Dihybrid cross

Involves two traits (e.g., TtGg x TtGg).

Punnett square

A diagram that shows the possible allele combinations in the offspring.

Phenotype ratio of Tt x Tt

3 dominant phenotype : 1 recessive phenotype.

Phenotype ratio of Tt x tt

1 dominant phenotype : 1 recessive phenotype.

Phenotype ratio of TtGg x TtGg

9 dominant for both traits : 3 dominant for one trait, recessive for the other : 3 recessive for one trait, dominant for the other : 1 recessive for both traits.