BIO EXAM 4

Prokaryote

- simple cells with nonmembrane bound organelles

- No nucleus, no mitochondria.

Eukaryote

cells with membrane bound organelles

binary fission

splitting or dividing into two identical parts

mitosis

process of cell division in sexually reproducing organisms

cytokinesis

- Division of cytoplasm

- Starts during anaphase or telophase

- Cell pinches apart

- Pinch crease (Cleavage furrow) is made of actin

- Plants: new cell plate forms in the middle, since cell walls are stiff

karyotype

visual representation of the complete set of chromosomes in a cell

chromosome

long DNA molecule with part or all of the genetic material of an organism

chromatin

mass of genetic material composed of DNA and proteins that condense to form chromosomes during eukaryotic cell division

centromere

region on a chromosome that joins sister chromatids

kinetochore

protein structure found on the centromere of each chromatid

contact inhibition

biological mechanism that controls or ceases cell growth and reproduction due to contact with adjacent cells

somatic cell

cells of the body that are not involved in reproduction

germ cell

cells of the body that give rise to the gametes (egg or sperm) of an organism that reproduces sexually

homologous

the similarity of the structure, position, or origin of different organisms

haploid

half the usual number of chromosomes

diploid

containing two complete sets of chromosomes (one from each parent)

asexual reproduction

generates genetically identical offspring that are the products of mitotic divisions (which type of reproduction is this?)

sexual reproduction

production of offspring through the union of male and female gametes

gamete

- sex cells

- egg and sperm

zygote

- the first cell of the new individual

- egg and sperm combine

sporophyte

- fertilization produces the diploid generation

- plant sex cell

gametophyte

- form positive and negative gametes by differentiation of some cells produced by mitotic division

- animal sex cells

allele

- versions of each gene

- Factors that govern the inheritance of each trait

gene

unit of heredity information that occupies a fixed position on a chromosome

gene pair

a pair of alleles. The two copies of a particular gene present in a diploid cell

locus

the physical location of a gene on a chromosome

true-breeding

the parents would produce offspring that would carry the same phenotype. Parents must be homozygous for every trait

hybrid

crosses between two different species, offspring contains 50% of genes from each parent species

homozygous

has the same versions (alleles) of a genomic marker from each biological parent

heterozygous

having different alleles for a particular trait

dominant

If heterozygous alleles are inherited, one is always expressed

recessive

a trait that is expressed only when genotype is homozygous

genotype

the genetic makeup of an organism // alleles carried by an organism

phenotype

an individual's observable traits determined by genotype and environment

segregation

half of the gametes carry a certain allele and the other half carries another allele

incomplete dominance

- Neither allele is dominant // crossing produces a third phenotype

- (2 gene, 2 pheno)

Codominance

- two alleles of the same gene are expressed equally in an organism

- (2 gene, 1 pheno)

Epistasis

- an unrelated gene modifies (or covers) the phenotype of another gene bc locus interact

- (interact = mod)

Polygenic trait

- multiple genes are expressed in one phenotype

- a characteristic that is influenced by two or more genes

- EX: skin and hair

pleiotropy

the expression of multiple traits by a single gene

Autosome

one of the numbered chromosomes, NOT a sex chromosome. Numbered based on size (23 total)

Sex chromosome

determine sex (XX=female) (XY = male), X is tall, Y is short

linkage

genes sit close together on a chromosome and are more likely to be inherited together

nucleic acid

biomolecule that stores and transmits genetic information in living organisms

nucleotide

fundamental building block of nucleic acid

dna

molecule that is the genetic material of most all living organisms

rna

molecule that forms a template for production of proteins

polymerase

an enzyme that catalyzes the formation of a polymer, especially DNA or RNA from precursor substances

nucleosome

the basic structural unit of DNA packaging in eukaryotes

histon

highly basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei

transcription

biological process wherein the mRNA transcript (i.e. copy of the coding sequence for a particular protein) is produced, generally by transcribing the template strand of DNA

translation

the process of converting the genetic information from mRNA into a sequence of amino acids or proteins

codon

a codon is a DNA or RNA sequence of three nucleotides

exon

coding region of a gene that contains the information required to encode a protein

intron

non coding DNA sequence within a gene that is not expressed in the final RNA or protein product

promoter

a region of DNA upstream of a gene that controls the expression of that gene by binding relevant proteins

Nondisjunction

the failure of homologous pairs to separate during the first meiotic division or of chromatids to separate during the second meiotic division

central dogma of biology

DNA -> RNA -> Protein

(flow of genetic information)

Be able to distinguish between a chromosome and chromatid

- Chromatid is a strand of DNA that splits from a chromosome during cell division

- Each chromosome contains 2 identical chromatids

Understand the process of binary fission in prokaryotes

- Prokaryotes split and reproduce (asexual)

- DNA replicates

- Cell Splits and divides into two parts with only one set of DNA each

Be able to distinguish between mitosis and meiosis.

- In mitosis, the chromosomes replicate and are divided into two new nuclei. The cell gets divided once into two daughter nuclei.

- In meiosis, a single cell divides twice to produce four cells

- Meiosis produces sex cells (gametes)

- Mitosis produces body cells

Be able to describe the phases of interphase

- G1 Phase - cells grow

- S phase - DNA replicates and chromosomal proteins are duplicated

- G2 Phase - cell growth continues and cells prepare for mitosis

Be able to describe the stages of mitosis, events that happen at each stage

- Please Pee on the MAT (c)

- Prophase

- Prometaphase

- Metaphase

- Anaphase

- Telophase

- Cytokinesis

Prophase

- Chromosomes condense

- Nucleolus disappears

Prometaphase

- Chromosomes condense more

- Nuclear envelope breaks down

- Chromosomes are released

- Mitotic spindle grows

- Microtubules of the mitotic spindle attach to the kinetochores of condensed chromosomes

Metaphase

- Chromosomes line up at metaphase plate

- Spindle checkpoint occurs here: cells check that all chromosomes are at the metaphase plate with kinetochores correctly attached to microtubules

Anaphase

- Sister chromatids separate and push to opposite sides (protein glue breaks down)

- Microtubules push poles apart

- Kinetochore microtubules pull chromosomes toward poles

- Driven by motor proteins

Telophase

- Spindle disappears

- Nuclear membrane reforms

- Nucleolus reappears

- Chromosomes decondense

What is the mitotic spindle? How do the components separate the chromosomes?

- Forms in prophase

- Forms between two centrosomes as they migrate toward the opposite ends of the cell

- Where they form spindle poles

- Made up of microtubule and motor proteins

What are the three mitotic checkpoints, and what is being checked at each?

- Between G1/S

- Between G2/M

- Metaphase checkpoint

Between G1/S

Decides if it will divide or not (is there damage to DNA and sufficient resources)

Between G2/M

Checks integrity of DNA that needs repair

Metaphase checkpoint

Are all the chromosomes lined up correctly on the metaphase plate

Plant cytokinesis

a cell plate forms between the daughter nuclei and grows laterally until it divides the cytoplasm in two

Animal cytokinesis

a furrow girdles the cell and deepens until it cuts the cytoplasm into two parts

outline of meiosis ( very basic)

- DNA is replicated

- Then meiosis has 2 divisions: Meiosis 1 and Meiosis 2

Meiosis 1 (end goal and steps)

- Replicated DNA is divided into daughter cells (Diploid to haploid)

Prophase 1

Metaphase 1

Anaphase 1

Telophase 1 + cytokinesis

Prophase 1

(1) chromosomes condense, nuclear envelope disappears, cross over happens

Metaphase 1

(1) Pairs of homologous chromosomes move to middle of cell

Anaphase 1

(1) homologous chromosomes move to opposite sides of the cell

Telophase 1 + cytokinesis

(1) Chromosomes gather at poles and cell divides

Meiosis 2 phases

Prophase II

Metaphase II

Anaphase II

Telophase II + Cytokinesis

prophase II

(2) new spindle forms around chromosomes

Metaphase II

(2) chromosomes line up at equator

Anaphase II

(2) centromeres divide, chromosomes move to opposite poles of the cells

Telophase II + Cytokinesis

(2) nuclear envelope forms around each set of chromosomes + cytoplasm divides

What is crossing over? When does it occur? Why does it occur?

- Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes

- during meiosis (prophase 1)

- results in new allelic combinations in the daughter cells.

- Maintains genetic diversity within a population and allows for recombination across generations

What is the mechanism and result of independent assortment of the chromosomes?

- Second major source of genetic variability in meiosis

- refers to the variation of chromosomes, or genetic information, during sex cell division

- allows for genetic differentiation in offspring

- In metaphase I, one of each homologous pair is randomly attached to the spindle of each pole

- The 23 chromosome pairs of humans allow 223 different combinations of maternal and paternal chromosomes

- Attaching the mixed up chromosomes to other ones randomly

Be familiar with the role and products of meiosis in animals as compared to plants

- Meiosis makes four haploid (half as many chromosomes as the parent cell) daughter cells

- The purpose of meiosis is to produce gametes, or sex cells

- Animals directly produce gametes by the process of meiosis

- Plants produce spores by meiosis

What did Mendel's monohybrid cross experiments demonstrate? (methods, results, and conclusions)

Methods // Results:

- Mendel crossed pollinated a pair of true breed pea plants with contrasting traits: one tall and another dwarf

- Genes can appear to skip a generation as a result of recessive inheritance

- The ratio of plants was 3 Tall : 1 Short

Conclusions:

- A pair of alleles determine inheritance

- If heterozygous, one allele is dominant over the recessive allele

- Principal of Segregation: alleles separate randomly when gametes are formed

What is meant by a testcross?

- A cross between an individual with the dominant phenotype and a homozygous recessive individual (C? x cc)

- Used to determine if the individual is homozygous (CC) or heterozygous (Cc)

What is a dihybrid cross? What did Mendel's dihybrid crosses demonstrate?

- Individuals that are heterozygous for the 2 allele pairs of 2 different genes

- Mendel crossed RRYY and rryy resulting in an F1 generation that was 100% RrYy

- The resulting F2 generation had a phenotypic ratio of 9:3:3:1

- This showed Mendel that the genotype for shape and the genotype for color did not have an affect on each other → independent assortment

- Independent Assortment Principal means alleles of genes that govern two characters assort independently during formation of gametes

What are Mendel's four postulates?

1) Principles of Paired Factors

2) Principle of Dominance

3) Law of Segregation or Law of Purity of Gametes // Mendel's First Law of Inheritance

4) Law of Independent Assortment // Mendel's Second Law of Inheritance

Principles of Paired Factors

Genes segregate equally into gametes such that offspring have an equal likelihood of inheriting either factor

Principle of Dominance

The presence of a dominant allele will always mask the presence of a recessive allele

Law of Segregation or Law of Purity of Gametes // Mendel's First Law of Inheritance

During the formation of gamete, each gene separates from each other so that each gamete carries only one allele for each gene

Law of Independent Assortment // Mendel's Second Law of Inheritance

The allele a gamete receives for one gene does not influence the allele received for another gene

Be able to show how to predict the probability of F1 and F2 generations of monohybrid and dihybrid crosses

F1: 1:3:1

F2: 9:3:3:1

multiple allele system

- 3 or more alleles determine a single trait

- Ex: blood type

complete dominance

- Occurs when one allele - or "version" - of a gene completely masks another

- One allele will always be dominant