mitosis

Cell division in prokaryotes

-Bacterial cells divide by a type of cell division called "binary fission". -This is how bacteria reproduce (Remember: bacteria cells are prokaryotes so they don't have nucleus i.e. no mitosis occurs)

The human life cycle

-Both nuclear divisions (mitosis and meiosis) are necessary in the human life cycle. -All human cells have a total of 46 chromosomes or 23 pairs: 23 inherited from the mother and 23 from the father n=23, 2n= 46

Meiosis

-Cell division in which the chromosome number is reduced. -The process of meiosis happens in two series of nuclear divisions, meiosis I and meiosis II, each one with several phases. - Meiosis is the other type of nuclear division in eukaryotes. - Meiosis occurs only in the sexual parts of an organism (example: in reproductive organs of humans) for reproduction. - Meiosis occurs in two parts (meiosis I and meiosis II) and each part has different phases. - After meiosis, four daughter cells are produced and they contain half the chromosome numbers as the parental cell -During meiosis II chromosomes may not separate normally and the resulting daughter cells may have an abnormal number (either an extra one, or one less)

mitosis

-Cell division in which the chromosome number stays the same - Mitosis occurs during growth, development and repair of all tissues - Mitosis occurs in different phases - After mitosis, two daughter cells are produced and they contain the same number of chromosomes as the parental cell

Mendel's law of segregation

-Each individual has two factors (genes) for each trait (i.e. two alleles). -The factors (genes) segregate (separate) during gamete formation.

Chromosomes

-Rod-like structure in the nucleus and that contains genes. • Each species has a characteristic number of chromosomes: Human cells = 46 chromosomes Corn cells = 20 chromosomes Crayfish cells = 200 chromosomes • This number of chromosomes is called the diploid number(2n), because it contains two of each type of chromosomes • Humans have 23 pairs of chromosomes: 2 x 23 = 46 - One member of the pair originates from the mother - The other member originates from the father

Effects of gene mutations

-What are the effects of gene mutations? 1) Malformation of the protein it encodes making it non-functional 2) Formation of a truncated (incomplete) protein thus unable to function properly -Remember that 'gene expression' is based on the genetic code, so a change in the code will result in an amino acid change. -Mutant proteins that result from the expression of mutant genes do not function properly. Example: mutant hemoglobin in 'sickle cell anemia'

Cytokinesis

-division of the cytoplasm following mitosis or meiosis -After nuclear division (mitosis or meiosis) is complete, cytokinesis follows and two daughter cells form

Crossing-over

-exchange of segments of genetic material between chromosomes. -During the first nuclear division (meiosis I), crossing-over between chromosomes takes place resulting in genetic recombination.

Genetic recombonation

-general term for the production of daughter cells containing genetic material different from the parents. -NOTE: both crossing-over and independent assortment introduce genetic recombination that helps ensure that no two offspring have the same combination of genes as the parents

Independent assortment

-independent segregation of chromosomes during meiosis I -During the first nuclear division (meiosis I), independent assortment of chromosomes also takes place resulting in genetic recombination. -Each one of these possible orientation of chromosomes will segregate (move) in different directions, resulting in daughter nuclei with different combination of parental chromosomes. -Independent-assortment generates different combinations of maternal and parental chromosomes

Development

-series of stages by which a zygote becomes an organism Example: zygote>embryo>fetus>baby -Human development continues throughout our life span baby>child>young adult>mature adult>elderly

Interkinesis

period of time between meiosis I and meiosis II during which no DNA replication takes place.

Multiple alleles inheritance

• Occurs when a trait is controlled by multiple alleles (more than two). But each person usually has only two of the possible alleles • Example: human blood types (A, B, AB, O) PHENOTYPE GENOTYPE A IAIA or IAi B IBIB or IBi AB IAIB O ii

Polygenic Inheritance

• Occurs when a trait is governed by two or more sets of alleles • Examples of traits resulting from polygenic inheritance are: size, height, shape, skin color, metabolic rate, and behavior • Polygenic traits are influenced by the environment

Incomplete dominance

• Occurs when the heterozygote is intermediate between the two homozygotes • Example: wavy hair

Mitosis 6 phases

1.Interphase 2.Early prophase 3.Late prophase 4.Metaphase 5.Anaphase 6.Telophase

Williams Syndrome

Loss of an end piece of chromosome 7

Polar body

Nonfunctional product of oogenisis produced by the unequal division of cytoplasm in females during meiosis; in humans the three of the four cells produced by meiosis are polar bodies.

Codominance

Occurs when alleles are equally expressed in a heterozygote

Sister chromatid

One of two genetically identical chromosomal units that are the result of DNA replication and are attached to each other at the centromere

Gamets

Produces and transports gametes (sex cells) Sperm = male gamete Egg = female gamete Sperm form in testis Eggs form in ovaries -Remember: gametes are produced by MEIOSIS

oogenesis

Production of eggs in females by the process of meiosis and maturation.

spermatogenesis

Production of sperm in males by the process of meiosis and maturation

Types of inheritance

There are several types of human inheritance: a) Simple dominant or recessive inheritance (example: widow's peak) b) Incomplete dominance c) Codominance d) Multiple allele inheritance e) Sex-linked inheritance f) Polygenic inheritance

Metaphase

Third phase of mitosis; chromosomes are aligned at the metaphase plate. (Metaphase plate is a disk formed during metaphase in which all of a cell's chromosomes lie in a single plane at right angles to the spindle fibers.)

Anticodon

Three-base sequence in a transfer RNA molecule base that pairs with a complementary codon in mRNA.

Codon

Three-base sequence in messenger RNA that during translation directs the addition of a particular amino acid into a protein or directs termination of the process

Transfer RNA

Transfer RNA (tRNA) carries amino acids to the ribosome to make proteins

Messenger RNA

Type of RNA formed from a DNA template and bearing coded information for the amino acid sequence of a polypeptide.

Haploid number, n

indicates only one of each kind of chromosome

Cell cycle

- Cells are alive and therefore they have a "lifetime" known as 'cell cycle' - The cell cycle is an orderly set of stages in eukaryotes that involves cell growth and nuclear division - The cell cycle is controlled by internal and external signals - There are 3 check-points where the cell cycle can be stopped if necessary (G1, G2, and M)

Karyotype

- a test to check chromosomes' structure and number

Apoptosis

-Apoptosis is a programmed cell death involving a cascade of specific cellular events leading to death and destruction of the cell - When a check-point determines the cell cycle is faulty and must stop, apoptosis is activated - Cancer is a disease characterized by unrestricted cell growth - Cancer results from a failure to control the cell cycle at the check points

Trait

A characteristic of an organism based on the physiology, morphology, or genetics

Cancer

Cancer is a failure of genetic control of a cell: • Mutations happen in genes that control cell growth • Cells become 'immortal' (they cannot regulate their growth) • Uncontrolled cell growth leads to the formation of unorganized group of cells called tumors • Cancer cells can detach from the tumor and spread to other parts of the body where they induce growth of new tumors • Cancer is caused by "inheritance" (genes inherited from parents), "environmental factors" (mutagens), or by viruses • Genetic tests are available for detection of some cancers that are inherited (example: breast cancer)

Centromere

Constriction where sister chromatids of a chromosome are held together.

Recall gene expression

DNA sequence Transcription RNA sequence Translation Protein sequence Because every living organism uses the same processes for gene expression, it is possible to make 'transgenic' organisms.

RNA polymerase

During transcription, an enzyme that creates an mRNA transcript by joining nucleotides complementary to a DNA template.

Embryonic germ layers

Ectoderm (outer layer) = Nervous system; epidermis of skin;epithelial lining of oral cavity and rectum. Mesoderm (middle layer) = Musculoskeletal system; dermis of skin; cardiovascular system; urinary system; reproductive system-including most epithelial linings; outer layers of respiratory and digestive systems. Endoderm (inner layer) = epithelial lining of digestive tract and respiratory tract, associated glands of these systems; epithelial lining of urinary bladder

Telophase

Final phase of miosis; daughter cells are located at each pole.

Prophase

First phase of mitosis; characterized by the chromatin; chromosomes are visible, but scattered in the nucleus

Chromatid

Following replication, a chromosome consists of a pair of sister chromatids, held together at the centromere; each chromatid is comprised of a single DNA helix.

Anaphase

Fourth phase of mitosis; chromosomes move toward the poles of the spindle. (spindle is Collection of microtubules that assist in the orderly distributiom of chromosomes during cell division)

Gene expression

Gene expression is the process by which genes (DNA) are converted to proteins and these proteins will have a specific function in an organism. The outcome of these proteins' function is the 'phenotype' of the organism. Example:-The pea plants that Mendel studied, have genes that encode for proteins that gives shape to the seed. -The round seeds "express" the gene that encodes for round shape. -The wrinkle seeds "do not express" the gene that encodes for round shape and thus the seed looks wrinkle. • The sequence of the bases in DNA specifies a gene • Gene is a segment of DNA that encodes the amino acid sequence of a protein • Gene expression involves two processes: - Transcription > conversion of DNA to RNA - Translation > conversion of RNA to protein • The sequence of bases in DNA and RNA encode a particular sequence of amino acids of a protein => gene expression is based on a 'genetic code'

Polygenic Inheritance and environmental effects

Height in humans is controlled by several sets of alleles and environmental factors are also involved.

Inv Dup 15 syndrome

Inverted duplication in chromosome 15

Genetic code

Specific combination of 3 bases, encodes a specific amino acid Codon=3 bases that encode an amino acid

Interphase

Stages of the cell cycle (G1, S, G2) during which growth and DNA synthesis occur when the nucleus is not actively dividing.

Ribsomal RNAs

Structual form of RNA found in the ribosomes.

Genome

Sum of all of the genetic information in a cell of organism

DNA Repilcation

Synthesis of new DNA double helix prior to mitosis and meiosis in eukaryotic cells and during prokaryotic fission in prokaryotic cells.

Phenotype

The appearance of an organism caused by the genotype and environmental influences, (Note: not all phenotypes are observable, for example 'low metabolism' are phenotypes that cannot be perceived by the human eye)

Human Devlopment

ZYGOTE > Mitosis and formation of germ layers = EMBRYO > Organ development from germ layers = FETUS > Organ systems formed = NEW BORN

Pedigree

a chart of a family's history with regard to a particular genetic trait

Recessive allele

allele expressed only in the homozygous recessive genotype. Represented with lowercase letters

Dominant Allele

allele that exerts its phenotype in the heterozygote; ir masks the expression of the recessive allele. Represented with capital letters.

Allele

alternative form of a gene; usually represented with a letter

Parent cell

cell that is going to divide. It has X number of chromosomes.

Homologous chromosomes

chromosomes with the same shape and that contain genes for the same trait.

Zygote

diploid cell formed by the union of sperm and egg.

Genotype

genes of an organism for a particular trait or traits

Gamete

haploid sex cedll like a sperm and egg

Homozygous

having identical alleles for a given trait (AA or aa)

Heterozygous

having two diggerent alleles for a given trait (Aa)

Diploid number, 2n

indicated two of each type of chromosome

Daughter Cell

the resulting cells from the division of the parental cell. It has the same X number of chromosomes as the parental cell.

Offspring

the resulting progeny (babies) of a genetic cross

Fertilization

union of sperm nucleus and egg nucleus to form a zygote

Gene mutations

• A gene mutation is a change in the sequence of bases (or nucleotides) within a gene Example: Normal gene sequence: ATG GGC CTC GGA ATT CCC AGG ......... Mutant gene sequence: ATG GGC CAC GGA ATT CCC AGG ........ • Mutations in genes can be caused by: 1) Errors in DNA replication during cell division (mitosis & meiosis), but these errors are rare 2) Environmental factors called mutagens such as UV light, X rays, radioactive elements, certain chemicals (pesticides) -Mutations can be introduced during DNA replication -Errors inserting the right nucleotide in the newly made DNA strand causes mutations -Certain chemicals can modify the nucleotides of DNA leading to mutations: Normal pairing of DNA bases: A with T only C with G only Some chemicals modified the G base and now it pairs with T instead of C:

DNA technology

• Also known as 'genetic engineering' or 'biotechnology' • Genetic testing • Gene therapy • DNA fingerprinting • Genetically Modified Organisms (GMOs)

Cell division

• Cells divide with the purpose of producing more cells 1) Mitosis - keeps same number of chromosomes 2) Meiosis - reduces the number of chromosomes by half • Eukaryotic cells have to types of divisions: The purpose of mitosis is growth and development The purpose of meiosis is reproduction

DNA

• DNA is the genetic material of living organisms • DNA is a long molecule made of nucleotides •DNA is a double helix made of two antiparallel polynucleotide chains held together by hydrogen bonds. • Four nucleotides (bases) make DNA molecule: Adenine (A) Guanine (G) Thymine (T) Cytosine (C) • The four bases can only pair this way: A with T only C with G only This is the nucleotide 'pairing rule'

DNA replication

• DNA replication = the process of copying one DNA helix into two identical helices • When cells divide, DNA is replicated (recall mitosis and meiosis) • The DNA double helix unwinds and unzips during DNA replication

How are genes inherited?

• Example: Inheritance of a single trait, "widow's peak" • In humans, widow's peak is a dominant trait: W = Widow's peak (dominant allele) w = Straight hairline (recessive allele)

How to figure out inheritance

• Genetic crosses are used to determine how genes from parents are passed on to their offspring . • Punnett square = gridlike device used to calculate the expected results of a genetic cross. -Determine the GENOTYPES and PHENOTYPES of all the offspring 1 WW > Homozygous dominant 2 Ww > Heterozygous 1 ww > Homozygous recessive

Genetic testing

• Genetic tests = tests that look for mutations in genes or changes in chromosome structures • Through genetic testing it is possible to detect the likelihood of cancer being present orto develop in the near future • Common genetic tests for: colon, bladder, breast, thyroid, and melanoma cancers • Genetic testing requires knowledge of the gene sequence

DNA fingerprinting

• Genome = is all the DNA that occurs in an organism's cells • The human genome has ~3 billion base pairs and ~20,000 genes • Because no two individuals have identical genome sequence, the genome is considered a 'fingerprint' or an ID • DNA fingerprinted is currently used for parental dispute identification and to solve crimes

Gene therapy

• It is the insertion of genetic material (genes) into human cells for the treatment of a disorder • Currently, cardiovascular diseases and cancer can be treated by gene therapy • Genes are administered to patience using viruses as 'vectors' to deliver them inside cells • Inside human cells, the gene gets "expressed" and the protein that encodes is made 1)DNA sequence (red) that corresponds to a normal human gene needed is inserted in virus chromosome 2)Virus infects a human cell such as a bone marrow stem cell 3)The normal human gene, carried by the virus, gets incorporated into a chromosome of the human cell

Sex-linked inheritance

• Sex-linked traits are traits controlled by the sex chromosomes • Humans have 23 pairs of chromosomes: 22 pairs are called autosomes 1 pair is called the sex chromosome • Human males > XY pair of sex chromosomes Human females > XX pair of sex chromosomes • Example of sex-linked trait: color blindness -The possible genotypes and phenotypes in males and females for color blindness are the following: XBXB = female who has normal color vision XBXb = female who has normal color vision but who carries a color blindallele (b) XbXb = female who is color blind XBY = male who has normal color vision XbY = male who is color blind Consider a male parent who has the enotype XBY and a female parent who has the XBXb. Both of them have normal color vision. Is it possible for them to have a child that is color blind?

Biotechnology

• Technology that make use of natural biological systems to create a product or achieve a particular result desired by humans • Biotechnology products can come from bacteria, plants, and animals • Transgenic organism = an organism (such as bacteria, plants, or animals) that have had a foreign gene inserted into them for expression • Transgenic organisms are also known as GMOs = genetically modified organisms Transgenic farm animals are used to produced pharmaceutical products secreted in their milk Examples: drugs for treatment of cystic fibrosis, cancer, blood diseases, etc 10 YEARS AGO Dolly was created! The first transgenic animal ENVIRONMENTAL CLEANUP Transgenic bacteria used to decontaminate toxic compounds from water and soil

Transcription

• The process that converts the DNA sequence of a gene into RNA sequence • Transcription happens in the nucleus of the cell • The new RNA molecule moves to the cytoplasm to be processed into a protein (translation) DNA double helix has to 'unwind' to convert DNA to RNA • The process that converts the RNA sequence of a gene into protein sequence • Translation happens in the cytoplasm of the cell Ribosomes are the factories where the RNA codons are read and the corresponding amino acid sequence synthesized to make the protein

Cloning

• The production of identical individuals • Two types of cloning: - Reproductive cloning - Therapeutic cloning • Reproductive cloning = the making of an individual that is identical to the original individual Examples: Dolly, bacteria, plants, etc • Therapeutic cloning = the making of mature cells of different types. These cells can be used to treat human illnesses such as diabetes, spinal cord injury, and Parkinsons disease.

RNA

•RNA is a single strand molecule (not double helix) made of nucleotides •The Four nucleotides (bases) in RNA are: Adenine (A) Guanine (G) Uracil (U) ‡ instead of T Cytosine (C)