AP Biology: Genetics

Cell Division

Process by which a cell divides into two new daughter cells

Parent Cell

original cell before cell division

Daughter Cells

The cells that are produced as a result of mitosis. These cells are identical to each other, and also to the original parent cell.

Process of Cell Division

mitosis and meiosis

The Cell Cycle

series of events that cells go through as they grow and divide

Interphase

Cell grows, performs its normal functions, and prepares for division; consists of G1, S, and G2 phases

G1 Phase

The first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins. Checkpoints: does the cell have enough energy?

Is it large enough?

Synthesis Phase

a cell's DNA is copied during this phase. at the end of this phase, each chromosome consists of two chromatids attached at the centromere. CDKs (cyclins/cycle dependent kinase) signal the division.

cyclins and cyclin-dependent kinases

The proteins that participate in the functioning of the checkpoints for cell cycle control are

G2 Phase

The second growth phase of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs.

Cell size/energy reserves are assessed. More importantly: have ALL chromosomes been replicated without mistakes and or damages?

M checkpoint (metaphase)

Check for whether chromosomes properly attached to spindle fibers

Mitosis

cell division in which the nucleus divides into nuclei containing the same number of chromosomes

Meiosis

Cell division that produces reproductive cells in sexually reproducing organisms

Prophase

first and longest phase of mitosis, during which the chromosomes become visible and the centrioles separate and take up positions on the opposite sides of the nucleus. Mitotic spindle forms fibers in cytoskeleton or centrioles. Kinetochores attach to the centromere. Spindle finished forming between the poles of the cell.

Metaphase

second phase of mitosis, during which the chromosomes line up across the center of the cell

Anaphase

the third phase of mitosis, during which the chromosome pairs separate and move toward opposite poles. Occurs rapidly. Kinetochore help pull the chromosomes to opposite poles.

Telophase

the final phase of cell division, between anaphase and interphase, in which the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed. spindle disassembles. Nucleolus appears.

Cytokinesis

Division of the cytoplasm during cell division

Chromatids

two identical chromosomes that split and contain the same genetic material. Must grow in size to be mature cells

Centromeres

the point on a chromosome by which it is attached to a spindle fiber during cell division.

Spindle Fibers

Protein structures which move the chromosomes during cell division.

Cell Checkpoints

A control point where stop and go signals regulate the cell cycle; G1 checkpoint, G2 checkpoint, M-Spindle checkpoint

Cytokinesis in Plant Cells

divide from inside out using a cell plate in middle of cell

Cytokinesis in Animal Cells

Cell membrane is drawn inward until the cytoplasm is pinched into two nearly equal parts

Cleavage forrow

splitting area where drawstring is pulled, breaking cell

Polar Microtubules

push the poles of the cell away from each other during mitosis

Mitotic Spindle

An assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis.

Karyokinesis

division of the nucleus

eukaryotic

A cell characterized by the presence of a nucleus and other membrane-bound organelles. Eukaryotes can be unicellular (protists) or multicellular (fungi, plants and animals).

Prokaryotic Cells

do not have a nucleus or other membrane-bound organelles

DNA Replication

DNA unzips into two parts and splits with the cell. In it's new home each side of the DNA strand attack to matching nucleotides to create 2 exact copies. It is important in puberty and other times of growth as it is the reproducing of your cells.

Process of DNA Replication

Enzymes unzip the DNA by breaking the hydrogen bonds between base pairs

The enzyme DNA polymerase joins individual nucleotides to form the complimentary strand to the existing DNA single strand

DNA polymerase also proof reads each new DNA strand to make sure each new molecule is an exact copy of the original DNA molecule

Helicase

An enzyme that untwists the double helix of DNA at the replication forks.

Primase

An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.

Polymerase

DNA polymerases are enzymes that create DNA molecules by assembling nucleotides, the building blocks of DNA. These enzymes are essential to DNA replication and usually work in pairs to create two identical DNA strands from one original DNA molecule.

Ligase

An enzyme that connects two fragments of DNA to make a single fragment

Enzymes

Catalysts for chemical reactions in living things

Nucleotides

Basic units of DNA molecule, composed of a sugar, a phosphate, and one of 4 DNA bases

Nucleic Acid

macromolecule containing hydrogen, oxygen, nitrogen, carbon, and phosphorus

Ribonucleic Acid

(RNA) single-stranded nucleic acid that contains the sugar ribose

Deoxyribose Nucleic Acid

the molecule that carries genetic information for the development and functioning of an organism. DNA is made of two linked strands that wind around each other to resemble a twisted ladder — a shape known as a double helix.

ribose sugar

sugar used in RNA to make up the "backbone"

Deoxyribose

A five-carbon sugar that is a component of DNA nucleotides. Ribose sugar has a hydroxyl (OH) group at position 2, whereas deoxyribose sugar has a hydrogen (H) atom at position 2

Nitrogenous Bases in DNA

adenine, guanine, cytosine, thymine

Nitrogenous Bases in RNA

Adenine, Uracil, Cytosine, Guanine

hydroxyl

OH-

Number of chromosomes

46 (23 pairs)

Okazaki Fragment

short segment of DNA synthesized discontinuously in small segments in the 3' to 5' direction by DNA polymerase

RNA Primer

short segment of RNA used to initiate synthesis of a new strand of DNA during replication

leading strand

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

lagging strand

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.

binding proteins

bind a specific substrate, either to sequester it in the body or hold its concentration at steady state

DNA backbone

Made of deoxyribose SUGAR and Phosphate

phosphoester bond

the linkage between the five prime sugar hydroxyl and a phosphate group

phosphodiester bond

the type of bond that links the nucleotides in DNA or RNA. joins the phosphate group of one nucleotide to the hydroxyl group on the sugar of another nucleotide

pyrimidines

cytosine, thymine, uracil

purines

Adenine and Guanine

Labelling Carbons

The carbon to the clockwise direction of the oxygen held within the ring structure of glucose is identified as the 1' carbon. The carbon clockwise of the 1' carbon is the 2' carbon, and so on.

polymer

A long molecule consisting of many similar or identical monomers linked together.

monomers

small unit that can join together with other small units to form polymers

carbohydrates

the starches and sugars present in foods

lipids

fats and oils

monomers in DNA

Nucleotides (sugar, phosphate, base)

the triplet code

A set of three-nucleotide-long words that specify the amino acids for polypeptide chains.

polypeptides

polymers of amino acids

amino acid structures

have a central carbon covalently bound to four parts

1) a hydrogen atom

2) an amino group

3) a carboxyl group

4) a side chain (R)

Bonds between nitrogenous bases

hydrogen bonds

Chargaff's Rule of Base Pairing

the percentage of A is equal to the percentage of T, and the percentage of G is equal to the percentage of C

Double helix structure

antiparallel strands of RNA

DNA mutation

When DNA changes (usually involves the bases)

Semiconservative Model of Replication

predicts that when a double helix replicates, each daughter molecule will have one old strand (derived or "conserved" from the parent molecule) and one newly made strand

Steps for DNA Replication

1) DNA unwinds and unzips

2) polymerase binds with the DNA strands and finds nucleotides to match to the bases

3) check errors in DNA strands

4) 2 identical strands of DNA twist up

RNA function

performs protein synthesis

protein synthesis

the formation of proteins by using information contained in DNA and carried by mRNA

mRNA

A type of RNA, synthesized from DNA, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.

DNA function

DNA is the code for making proteins and stores genetic information

kinetochore

A specialized region on the centromere that links each sister chromatid to the mitotic spindle.

asters

Microtubules and fibers that radiate out from the centrioles.

metaphase plate/equator

the region of the spindle in the middle of the cell along which the chromatids line up

cleavage furrow

The first sign of cleavage in an animal cell; a shallow groove in the cell surface near the old metaphase plate.

How do chromosomes form?

A single length of

DNA is wrapped many

times around lots of

proteins called

histones, to form

structures called

nucleosomes.

These nucleosomes

then coil up tightly to

create chromatin loops.

The chromatin loops

are then wrapped

around each other to

make a full

chromosome.

chromosome

a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

genes

basic unit of heredity in a living organism

contains the code for a single protein (enzyme)

The enzyme causes a chemical reaction that allows a

trait to be expressed (hair/eye colour, etc)

Genes hold the information to build and maintain

an organism's cells and pass genetic traits to

offspring

E.g. Gene for eye colour

alleles

Different forms of a gene

homozygous

An organism that has two identical alleles for a trait

heterozygous

An organism that has two different alleles for a trait

loci

Location of a gene on a chromosome

homologous chromosomes

Chromosomes that are paired - *diploid (next

slide ☺)

alike with regard to size and also position of the

centromere

also have the same genes (e.g. eye colour), but

not necessarily the same alleles (e.g. blue vs

brown), at the same locus or location

Pairs of chromosomes that are similar but NOT

identical based on:

Length

Centromere location

Banding patterns (when dyed)

Carry genes for the same trait at the same

location

tetrad

Each pair of homologous chromosomes.

Chromatids of homologous chromosomes are

aligned length wise, so that genes of one are

adjacent to corresponding genes on the other

Therefore a total of 4 chromatids

ploidy numbers

Number of sets of chromosomes in a biological cell (46 in humans)

diploid

(genetics) an organism or cell having two sets of chromosomes or twice the haploid number. homologous

chromosomes

one of the pair being

derived from the ovum

and the other from the

sperm

2n = 46

haploid

Having only one copy of

every chromosome

Example: father's X

chromosome is in one

sperm cell, and y

chromosome goes to

another sperm cell

n = 23

gamete

specialized sex cell such as an egg or a sperm,

which is haploid (n)

Has only half the number of chromosomes (23 in

humans)

A male gamete and a female gamete fuse and produce

a diploid zygote which develops into a new individual.

sex chromosomes

Chromosomes that determine the sex of an individual

1 pair out of 23

Called X and Y, determine individual's sex

Female XX, male XY

autosomes/somatic chromosomes

Any chromosome that is not a sex chromosome

karyotype

A photograph of the chromosome pairs of a cell arranged by size and shape.

preparing a karyotype

Sample cell in metaphase, chromosomes stained,

revealing banding patterns, then sorted and paired

homologous

term used to refer to chromosomes that each have a corresponding chromosome from the opposite-sex parent

sister chromatids

Identical copies of a chromosome; full sets of these are created during the S subphase of interphase.

oogenesis

the production, growth, and maturation of an egg, or ovum