M5 DNA & Genetics

Deoxyribonucleic acid (DNA)

The molecule of heredity, common to all life forms, which is passed from parents to offspring.

chromosome

A single, large DNA molecule, wound around proteins. They are located in the nuclei of eukaryotic cells.

Nucleotide

The building blocks of DNA. Each consists of a sugar, a phosphate group, and a base. The sequence of nucleotides along a DNA strand is unique to each person.

Double helix

The spiral structure formed by 2 strands of DNA nucleotides held together by hydrogen bonds.

possible nucleotide bases (4)

(A) adenine, (T) thymine, (G) guanine, (C) Cytosine

DNA Replication

The natural process by which cells make an identical copy of s DNA molecule.

Complementary

Fitting together; 2 strands of DNA are said to be complementary in that A in one strand always pairs with T in the other strand, & G always pairs with C.

Helicase

An enzyme that unwinds & unzips the DNA double helix during DNA replication.

DNA polymerase

An enzyme that “reads” the nucleotide sequence of a DNA strand & incorporates complementary nucleotides into a new strand during DNA replication.

semiconservative

DNA replication is said to be semiconservative because each newly made DNA molecule has 1 original DNA strand & 1 new DNA strand.

Polymerase Chain Reaction (PCR)

a laboratory technique used to replicate & thereby amplify, a specific DNA segment.

Genome

1 complete set of genetic instructions encoded in the DNA of an organism.

Short Tandem Repeats (STR)

Sections of a chromosome in which short DNA sequences are repeated.

Gel electrophoresis

A laboratory technique that separates fragments of DNA by size.

CODIS (Combined DNA Index System)

A computer database where, since 1994, the federal government has been collecting & storing DNA profiles of criminal offenders.

Cell Division

The process by which a cell reproduces itself; cell division is important for normal growth, development, maintenance, & repair of an organism.

cell cycle

The ordered sequence of stages through which a cell progresses to divide. The stages include preparatory phases (G1, S, G2) & division phases (mitosis & cytokinesis)

Interphase

The stage of the cell cycle in which dividing cells spend most of their time, preparing for cell division. There are 3 distinct subphases: G1, S, & G2.

Interphase: G1

Cell grows larger & begins to produce more cytoplasm & organelles.

Interphase: S

Cell’s DNA is replicated (chromosomes are duplicated)

Sister chromatids

the 2 identical DNA molecule that result from the replication of a chromosome during the S phase.

Interphase: G2

The cell prepares to enter the division phase.

2 division phases of cell cycle

mitosis & cytokinesis

Mitosis

The segregation & separation of replicated chromosomes during cell division.

Cytokinesis

the physical division of a cell into 2 daughter cells.

G0

resting phase of cell cycle

Carcinogens

Any substance that causes cancer. Most carcinogens are mutagens.

cell cycle checkpoints

A cellular mechanism that ensures that a stage of the cell cycle is completed accurately.

Apoptosis

A type of cell death; often referred to as cellular suicide.

Tumor

A mass of cells resulting from uncontrolled cell division.

centromere

the specialized region of a chromosome where the sister chromatids are joined; it is critical for proper alignment & separation of sister chromatids during mitosis.

miotic spindle

the microtubule-based structure that separates sister chromatids during mitosis.

phases of mitosis

prophase, metaphase, anaphase, telophase

prophase

• replicated chromosomes begin to coil up.

• the nuclear membrane begins to disassemble

• microtubule fibers begin to form the miotic spindle.

metaphase

• microtubule spindle fibers from opposite ends of the cell attach to the sister chromatids of each chromosome.

• replicated chromosomes become aligned along the middle of the cell.

anaphase

microtubules shorten, pulling the sister chromatids to opposite ends of the cell.

telophase

• identical sets of chromosomes reach each pole.

• microtubule spindle fibers disassemble

• a nuclear membrane forms around each set of chromosomes, forming the daughter cell nuclei.