nucleotides
The small units, or monomers, that make up DNA
double helix
Shape of DNA
Base pair rules for DNA
A-T (adenine-thymine); G-C (guanine-cytosine)
Rosalind Franklin
Woman who generated x-ray images of DNA, she povided Watson and Crick with key data about DNA
Watson and Crick
Developed the double helix model of DNA.
Maurice Wilkins
Used X-ray crystallography to study the molecular structure of DNA. Worked with Franklin (did not collaborate well) to create a picture of the DNA molecule which allowed Watson and Crick to deduce the double helix structure of two strands.
DNA replication
The process in which DNA makes a duplicate copy of itself.
DNA polymerase
a group of enzymes that bond the new nucleotides together
Helicase
An enzyme that untwists the double helix of DNA at the replication forks.
Ligase
An enzyme that connects two fragments of DNA to make a single fragment
Leading strand of DNA
the new complementary DNA strand built continuously along the template strand toward the replication fork in the 5' to 3' direction
Lagging strand of DNA
Strand of DNA built in short segments that are later joined. The lagging strand always moves away from the replication fork and lags behind building of the leading strand. (3-5 direction)
Okazaki fragments
Small fragments of DNA made on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.
Primase
An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.
cell cycle
the regular pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cells
Gap 1 (G1)
cells grow, carry out normal functions, and replicate their organelles
Synthesis Stage
DNA is replicated
Gap 2 (G2)
Additional growth happens and the cell prepares for mitosis
Mitosis
the division of the cell nucleus and its contents
Cytokinesis
the process that divides the cell cytoplasm
Chromosomes
one long continuous thread of DNA that consist of numerous genes along with regulatory information.
histones
protein molecules around which DNA is tightly coiled in chromatin
Chromatin
long strands of DNA found in the eukaryotic cell nucleus; condense to form chromosomes
Centromere
Area where the chromatids of a chromosome are attached
Chromatid
one half of a duplicated chromosome
telomeres
Repeated DNA sequences at the ends of eukaryotic chromosomes.
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
metaphase
phase of mitosis in 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
telophase
After the chromosome seperates, the cell seals off, Final Phase of Mitosis.
Cytokenisis (Mitosis)
The cytoplasm divides, in animal cells the cell membrane pinches inward, and in plant cells vesicles from the Golgi apparatus form a cell plate
cancer
A disease in which some body cells grow and divide uncontrollably, damaging the parts of the body around them.
benign
mild, not cancerous
malignant
cancerous
metastasize
the process by which cancer spreads from one place to another
somatic cells
also called body cells, make up most of your body tissues and organs
Gametes
are sex cells - ova, or eggs, in the female, and spermatozoa, or sperm cells, in the male.
homologous chromosomes
Pair of chromosomes that are the same size, same appearance and same genes.
autosomes
chromosomes that contain genes for characteristics not directly related to the sex of an organism
sex chromosomes
Chromosomes that determine the sex of an individual (X and Y chromosomes)
sexual reproduction
involves the fusion of two gametes, resulting in offspring that are a genetic mixture of both parents
Fertilization
the actual fusion of an egg and a sperm cell
Diploid
a cell has two copies of each chromosome: one copy from the mother, and one copy from the father. Represented as 2n.
Haploid
Cell that has only one copy of each chromosome. Represented as n.
Meiosis
a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.
Meiosis I: Prophase I
The nuclear membrane dissolves.
Chromatin tightly coils up.
Homologous chromosomes, each composed of two sister chromatids, come together. Chromatids of homologous chromosomes exchange segments in a process called crossing over.
Meiosis I: Metaphase I
During metaphase I of meiosis, paired homologous chromosomes line up across the center of the cell.
Meiosis I: Anaphase I
Homologous pairs separate and move toward opposite poles of the cell
Meiosis I: Telophase I
Duplicated chromosomes have reached the poles. Usually, cytokinesis occurs along with telophase.
Meiosis II: Prophase II
Chromosomes condense again and become visible. Spindle fibers again form. Nuclear membrane disintegrates again.
Meiosis II: Metaphase II
Duplicated chromosomes align at the cell equator like they are in mitosis.
Meiosis II
the second phase of meiosis consisting of chromatids separating, along with the two diploid cells splitting in two
Meiosis II is similar to mitosis in that
sister chromatids separate during anaphase
Karyotype
A display of the chromosome pairs of a cell arranged by size and shape.
Klinefelter syndrome
A chromosomal disorder in which males have an extra X chromosome, making them XXY instead of XY.
Monosomy X, called Turner syndrome
In females who have Turner syndrome, one copy of the X chromosome is missing, partially missing or changed.
Trisomy 21 (Down Syndrome)
Genetic disorder resulting from the presence of 3 #21 chromosomes; characterized by heart and respiratory defects and varying degrees of metal retardation
females have ____ chromosomes
XX
males have ____ chromosomes
XY