BIO FINAL

eukaryotic cell cycle

G1 (growth), S (DNA synthesis), G2 (preparation for division), M (mitosis), cytokinesis.

binary fission

A form of asexual reproduction used by prokaryotes: the cell grows, replicates its DNA, and splits into two identical cells.

Chromatid

one of two identical halves of a duplicated chromosome

chromosome

can be single or duplicated.

Sister chromatids

identical and joined at a centromere

homologous chromosomes

the same type but from different parents.

Centromere

joins sister chromatids

centrosome

an organelle that organizes spindle fibers.

Phases of mitosis

prophase, Metaphase, Anaphase, Telophase.

prophase

Chromatin condenses, spindle fibers form, nuclear envelope breaks down.

metaphase

Chromosomes align at the metaphase plate.

anaphase

Sister chromatids are pulled apart to opposite poles.

telophase

Nuclear membranes reform, chromosomes decondense.

Cytokinesis in animal cells

form a cleavage furrow

cytokinesis in plant cells

form a cell plate.

Function of mitosis

Growth, repair, and asexual reproduction in eukaryotes.

Checkpoint

Control points that regulate progression through the cycle, includes G1, G2, and M checkpoints.

G1 checkpoint

Checks for cell size, nutrients, growth factors, and DNA damage.

G2 checkpoint

Checks for DNA replication completeness and damage.

M checkpoint

Checks spindle attachment to kinetochores before anaphase.

cancer

Uncontrolled cell division due to loss of cell cycle regulation.

tumor

A mass of abnormal cells that can be benign or malignant.

Benign tumor

a tumor that stays in place

malignant tumor

invades tissues and can metastasize.

characteristics lost in cancer cells

Anchorage dependence and density-dependent inhibition.

transformation

Conversion of a normal cell into a cancerous one.

Prophase I

Homologous chromosomes pair up and crossing over occurs.

Metaphase I

Tetrads align at metaphase plate.

Anaphase I

Homologous chromosomes separate.

Telophase I

Two haploid cells with duplicated chromosomes are formed.

Meiosis II

Sister chromatids separate.

Meiosis

Four genetically unique haploid gametes.

genetic variation

Crossing over, independent assortment, random fertilization.

Crossing over

occurs during Prophase I of meiosis.

Independent assortment

occurs during

Metaphase I of meiosis.

random fertilization

Any sperm can fuse with any egg, increasing variation.

Law of Segregation

Alleles separate during gamete formation (Anaphase I).

Law of Independent Assortment

Genes on different chromosomes assort independently (Metaphase I).

Monohybrid cross

Cross involving one trait (e.g., Aa × Aa)

Dihybrid cross

Cross involving two traits (e.g., AaBb × AaBb).

Testcross

Cross to determine unknown genotype using a homozygous recessive individual.

Complete dominance

One allele completely masks the other.

Incomplete dominance

Heterozygous phenotype is a blend (e.g., red × white = pink).

Codominance

Both alleles are expressed (e.g., AB blood type).

Multiple alleles

More than two allele options in population (e.g., ABO blood types).

Pleiotropy

One gene affects multiple traits (e.g., sickle cell disease).

Epistasis

One gene affects the expression of another (e.g., Labrador coat color).

Polygenic inheritance

Multiple genes influence a trait (e.g., skin color).

Linked genes

Genes located close together on a chromosome and inherited together.

X-inactivation

Random inactivation of one X chromosome in females (Barr body).

nondisjunction

Failure of chromosomes to separate during meiosis. Gametes with abnormal chromosome numbers

ABO blood types

shows both codominance and multiple alleles.

one from each parent

How many alleles can a diploid organism inherit?

pedigree chart

traces inheritance of traits through generations.

Autosomal recessive traits

Can skip generations, both sexes equally affected, carriers exist

sutosomal dominant traits

Appears in every generation, both sexes affected, no carriers

X-linked recessive

more common in males, carrier females (XAXa) can have affected sons (XaY), affected females must have affected father and carrier or affected mother

X-linked recessive carriers

carriers can only females

no (hemizygous)

Can males be carriers of X-linked traits?

No

Can two affected autosomal recessive parents have unaffected children?

Yes

Can two affected autosomal dominant parents have unaffected children?

linked genes

Genes located close together on the same chromosome, often inherited together.

recombination

can occur during crossing over in Prophase I of meiosis.

recombination frequency

(# of recombinant offspring) / (total offspring)

linkage map

A diagram showing the relative positions of genes based on recombination frequencies.

Increases

As distance between genes increases, recombination frequency…

X-inactivation

Random inactivation of one X chromosome in females to balance gene expression.

Barr body

The inactive X chromosome in female cells.

nondisjunction

Failure of homologous chromosomes (in Meiosis I) or sister chromatids (in Meiosis II) to separate.

Aneuploidy

One extra or one missing chromosome (e.g., 2n+1 or 2n–1)

Polyploidy

More than two full sets of chromosomes (e.g., 3n, 4n)

chromosomal deletion

Loss of a segment of a chromosome.

chromosomal duplication

Repetition of a segment.

chromosomal inversion

Reversal of a segment within a chromosome.

chromosomal translocation

Segment moves from one chromosome to another non-homologous one.

Cri-du-chat syndrome

deletion on chromosome 5

Chronic Myelogenous Leukemia

reciprocal translocation between chromosomes 9 and 22

Griffith experiment

Discovered transformation in bacteria using S and R strains.

Avery, MacLeod, McCarty

Identified DNA as the transforming factor in bacteria.

Hershey and Chase

Used radioactive labeling to show DNA is the genetic material.

Chargaff's Rules

%A = %T and %G = %C; base pair ratios vary by species.

Rosalind Franklin

Used X-ray diffraction (Photo 51) to reveal DNA's helical shape.

Watson and Crick

Built double helix model of DNA using Franklin's photo.

Meselson and Stahl

Demonstrated DNA replication is semiconservative.

Antiparallel

Describes DNA strands running in opposite 5' to 3' directions.

Hydrogen bonds

Hold base pairs together: A-T (2), G-C (3).

Phosphodiester bond

Connects 3' and 5' carbons of adjacent nucleotides.

Purines

Double-ring bases: Adenine and Guanine.

Pyrimidines

Single-ring bases: Cytosine and Thymine (Uracil in RNA).

Helicase

Unzips DNA by breaking hydrogen bonds.

Topoisomerase

Relieves supercoiling ahead of replication fork.

Single-strand binding proteins

Stabilize separated DNA strands.

Primase

Lays down RNA primers to initiate DNA synthesis.

DNA polymerase III

Adds new DNA nucleotides to growing strand.

DNA polymerase I

Replaces RNA primers with DNA.

DNA ligase

Seals gaps between Okazaki fragments.

Okazaki fragments

Short DNA fragments on lagging strand.

Telomerase

Extends telomeres in germ/stem cells to prevent shortening.

Mismatch repair

Corrects errors missed by DNA polymerase proofreading.