BSC2010 Exam 4 USF

chromosome theory of inheritance

-Mendelian genes have a specific loci (Positions) on chromosomes

- Chromsomes undergo segregation and independent assortment

law of segregation

Alleles for each gene separate during gamete formation.

law of independent assortment

the law that states that genes separate independently of one another in meiosis

Thomas Hunt Morgan

Bred fruit flies, and supported the the theory of chromosomal inheritance by finding that a specific gene is carried on a specific chromosome

wild type

the phenotype for a character most commonly observed in natural populations

mutant

traits alternative to the wild type, We call them mutants because presumably these different forms arose from mutations, or changes, in the genetic material.

SRY gene

sex determining region of the Y chromosome, codes from protein that directs the development of anatomical features

Human Y chromosome

The Y chromosome is much smaller and simpler than the X chromosome, containing only 78 genes, compared to the 1,100 of the X chromosome.

Ovum

Carry X chromosome

Sperm

Carry X or Y chromosome, male determines sex

X-0 system

in grasshoppers, cockroaches, and other insects; males have only 1 sex chromosome (X) and female have 2 (XX); sex of the offspring is determined by whether the sperm cell contains an X chromosome or no sex chromosome

The Z-W System

The sex chromosome inheritance system in species in which the male is homogametic (ZZ) and the female is heterogametic (ZW). Mother determines sex

haplo-diploid system

A sex determination system in most species of bees and ants in which there are no sex chromosomes. Females develop from fertilized eggs (diploid) and males develop from unfertilized eggs (haploid).

sex-linked gene

gene located on the X or Y chromosome

Y-linked genes

genes found on the Y chromosome, theres few of these, Has mainly genes related to sex determination

X-linked genes

genes found on the X chromosome;

- X chromosome has many characters unrelated to Sex determination.

- For a recessive trait, a female needs two copies of the allele(XX), while males need one (XY)

- Males attract more X-linked gene disorders

X-linked disorders

hemophilia, colorblindness, duchenne muscular dystrophy

Duchenne muscular dystrophy

A human genetic disease caused by a X-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue.

Hemophilia

x-linked recessive disorder, affects mostly men

Barr Body (Drumstick Body)

A dense body formed from a deactivated X chromosome. Females therefore have a 50% chance of producing a gene if heterozygous for it

linked genes

Genes located on the same chromosome that tend to be inherited together in genetic crosses.

- Closely located genes tend to appear together when crossing, whether recessive or dominant.

- Do not separate independently.

genetic recombination

The regrouping of genes in an offspring that results in a genetic makeup that is different from that of the parents.

parental type offspring

Look exactly like one of the two parents, 50% chance

crossing over

the mechanism that breaks linked genes, genes close together travel together

-

random fertilization

increases even further the number combinations that can be produced

- ground work for natural selection, whichever recombinant trait confers a survival advantage will be passed on to more generations

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate. One gamete receives two of the same type of chromosome while another gamete receives no copy

Aneuploidy

Abnormal number of chromosomes due to nondisjunction in gamete formation.

Either short or has extra chromosome. Main reason for miscarriage.

Aneuploidy can also occur in mitosis. If this occurs in early embryonic development, the effects will be similar to nondisjunction in meiosis I or meiosis II.

monosomic zygote

has only one copy of a particular chromosome

trisomic

A chromosomal condition in which a particular cell has an extra copy of one chromosome, instead of the normal two it has three. Ex. Down Syndrome

Polyploidy

condition in which an organism has extra sets of ALL chromosomes.

Normal occurrence in plants, not animals.

triploid

3n

Tetreploid

4n

Deletion

A change to a chromosome in which a fragment of the chromosome is removed.

Duplication

repeats a segment

Inversion

reverses orientation of a segment within a chromosome

Translocation

Change to a chromosome in which a fragment of one chromosome attaches to a nonhomologous chromosome.

alterations of chromosome structure

These types of errors may be caused by radiation damage, toxin exposure, or errors in meiosis.

syndrome

A group of symptoms typical of a particular disease or condition

Down Syndrome

•an aneuploid condition that results from three copies of chromosome 21

Klinefelter syndrome

•result of an extra chromosome in a male, producing XXY individuals, Sterile, Sub-normal IQ, female Sex characters

Turner Syndrome

A chromosomal disorder in females in which either an X chromosome is missing, making the person XO instead of XX, or part of one X chromosome is deleted. Makes females sterile because sex organs never mature.

Cri du chat syndrome

deletion of short arm of chromosome 5, mentally retarded, cry like a cat

Chronic Myelogenous Leukemia (CML)

caused by translocations of chromosomes 9 and 22, cells are stimulated to divide and soon overwhelm the normal blood components.

genomic imprinting

a phenomenon in which expression of an allele in offspring depends on whether the allele is inherited strictly from either the male or female parent.

Result of methylation (addition of CH3)

extranuclear genes

Genes outside the nucleus, in the mitochondria and chloroplasts, comes from the egg

Extranuclear caused diseases

Mitochondrial myopathy( Muscle Deterioration)

Leber's hereditary optic neuropathy (Sudden blindness)

- Muscular and nervouse system are affected by abnormal ATP production

Gleevac (Imatinib mesylate)

•Gleevacis a drug that targets this aberrant protein kinase

•Blocks ATP binding on kinase and prevents activation

•90% of CML patients treated with Gleevacshow complete remission of disease

Hemophilia

An X-linked recessive disorder in which blood fails to clot properly, leading to excessive bleeding if injured.

James Watson and Francis Crick

introduced double-helical model for DNA, recognized pattern that Franklin provided

viruses and bacteria

Used to discover the role of DNA, cheap and easy to work with

Transformation

process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria

- a change in genotype and phenotype due to assimilation of foreign DNA

Federick Griffith

Found that some chemical factor from heat- killed bacteria of one strain could change the inherited characteristics of another strain

bacteriophages (phages)

viruses that exclusively infect bacteria

Alfred Hershey and Martha Chase

used radioactive markers in experiments to show that DNA was the genetic material in cells (Sulfur- Protein, phosphurus- DNA)

Chargaff's Rule

- [A]=[T] and [G]=[C], they pair up across from one another forming two strands also called base pairing.

- Base composition of DNA varies between species.

Rosalind Franklin

- Woman who generated x-ray images of DNA, she povided Watson and Crick with key data about DNA

- Deduced the sugar-phosphate was on the outside, whilst the nitrogenous bases were on the inside

- deduced Purines paired with pyrimidine

Chargaff rule in action

If we find that a particular DNA strand has 36% As, then by Chargraff'sRules, we know it must also have 36% Ts.

36% + 36% = 72%

100%-72% = 28%, meaning that there must be 14% Gs and 14% Cs.

semiconservative replication

Method of DNA replication in which parental strands separate, act as templates, and produce molecules of DNA with one parental (old)DNA strand and one new DNA strand

antiparallel strands

The structure of DNA is antiparallel, which means there are to strands parallel to each other going in opposite directions.

DNA polymerases add nucleotides only to free 3' end of a growing strand

origins of replication

Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides. Opens up a replication "bubble".

Eukaryotic cells may have 100s or 1000s of origins of replication.

Prokaryotic cells usually have 1. Proceeds in both directions.

replication fork

A Y-shaped region on a replicating DNA molecule where new strands are growing.

Helicases

An enzyme that untwists the double helix of DNA at the replication forks, separating the two strands and making them available as template strands.

single strand binding proteins

bind to and stabilize single-stranded DNA

Topoisomerase

corrects "overwinding" ahead of replication forks by breaking, swiveling, and rejoining DNA strands. Without them, DNA would break at random locations and cause errors.

short RNA primer

The initial nucleotide strand is a_______. C

DNA polymerase

Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule.

- Cannot start, only add on to existing chain

-Bacteria produce faster but have more errors

- Human cells are slower but more accurate, and roughly equivalent due to the multiple replication sites.

Primase

An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template. makes starting point for DNA polymerase. RNA uses U instead of T

leading strand

The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.

lagging strand

The strand that is synthesized in fragments using individual sections called Okazaki fragments. Primer still needed. DNA polymerase starts later in fork because there is no room closer. Repetitively used RNA primer. Primer is removed later and replaced with DNA

Okazaki fragments

Short fragments of DNA that are a result of the synthesis of the lagging strand during DNA replication. Joined together by DNA ligase.

DNA ligase

A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain.

DNA replication machine

may be stationary during the replication process

Proofreading

mispaired nucleotide is replaced by DNA polymerase. First level

mismatch repair

The cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides. Second level.

Nucleotide Excision Repair (NER)

a nuclease cuts out and replaces damaged stretches of DNA

nuclease

A DNA cutting enzyme that excises damaged DNA.

Mutation

When errors aren't fixed during proofreading in DNA. Ground work for natural selection. If negative, will most likely be eliminated from population because it makes offspring less fit to live, so they can't reproduce.

end replication problem

RNA primer at end cannot be replaced with polymerase--> DNA is lost. Gets shorter and shorter.

Telomeres

Repeated DNA sequences at the ends of eukaryotic chromosomes that prevent the loss of genes. Shortening of telomeres pertains to aging.

Telomerase

An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells. Helps maintain the length unlike in humans. In cancer cells to help them keep growing.

Nucleoid

A dense region of DNA in a prokaryotic cell. DNA is "supercoiled"

Chromatin

Clusters of DNA, RNA, and proteins in the nucleus of a cell, eukaryotic cells

Chromatin Packaging in Eukaryotic Chromosome:

First Level

Due to histones, special proteins that associate with the DNA double helix; have strong positive charge so they are highly attracted to the negative charge of DNA

Chromatin Packaging in Eukaryotic Chromosome:

Second level

nucleosomes; consist of a core of 8 histone proteins, around which a segment of DNA is wrapped twice. resemble beads, which is why models are called beads on a string

Chromatin Packaging in Eukaryotic Chromosome:

third Level

30-nm fiber result of the histone tails of the 10-nm fiber and adjacent linker DNA.

Chromatin Packaging in Eukaryotic Chromosome:

Fourth Level

300-nm fiber, This is formed as the 30-nm loops around a protein scaffold consisting of mostly histones and topoisomerase.

metaphase chromosome

the most compact and highest level of packaging. Somehow the 300-nm fibers loop and fold around one another in a very precise manner, such that genes always end up in the same location on the chromosome. How this occurs is still a mystery.

At interphase

•some chromatin is organized into a 10-nm fiber, but much is compacted into a 30-nm fiber, through folding and looping

Euchromatin

The less condensed form of eukaryotic chromatin that is available for transcription. Active.

Heterochromatin

Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed. makes it difficult for the cell to express genetic information coded in these regions.

Histones

•Histones can undergo chemical modifications that result in changes in chromatin organization

•These changes can result in changes in gene expression

•Histones are very important not just for packaging DNA, but also for regulating how genes are expressed

gene expression

the process by which DNA directs the synthesis of proteins

Transcription

synthesis of an RNA molecule from a DNA template

- Produces messeger RNA(mRNA)

- First stage of gene expression

Translation

synthesis of a polypeptide, using information in the mRNA

Archibald Garrod

first suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions

- Inborn errors of metabolism; symptoms of inherited disease reflect an inability to synthesize a certain enzyme

one gene-one polypeptide hypothesis

The premise that a gene is a segment of DNA that codes for one polypeptide.

Messenger RNA (mRNA)

A type of RNA, synthesized from DNA and attached to ribosomes in the cytoplasm; it specifies the primary structure of a protein. Carries information from DNA to protein. (Construction foreman)

Ribosomes

site of translation (Construction site)

- free ribosomes synthesize protein that function in cytosol

- bound ribosomes mostly synthesize proteins that are secreted from cell

Central Dogma

theory that states that, in cells, information only flows from DNA to RNA to proteins

primary transcript

An initial RNA transcript from any gene; also called pre-mRNA when transcribed from a protein-coding gene.