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BIO_SC 1010: Chromosomes
Chromosomes |
one long DNA molecule wrapped around a series of proteins found in cells |
Four Types of Nucleotides and what bases they bond with |
A= Adenine :: T= Thymine
--> C= Cytosine :: G= Guanine |
Purpose of DNA |
-instructs cells to make proteins.
- made out of a long strand of amino acids and the structure and function of protein is determined by the order of its amino acids - the order of amino acids is determined by the order in which ATC & G occur on the chromosome |
Gene |
a segment of DNA specifying the sequence of amino acids in a single protein |
Mutation |
a change in the sequence of bases in DNA
-cause frame shifts in reading the codons -all codons 'downstream' are affected -protein is likely to be dysfunctional |
Point Mutation |
one base changes to another |
Insertion or deletion |
One (or more) bases is inserted/removed |
Gene Duplication |
- large chunk of DNA is duplicated within the strand |
What causes mutations? |
-high energy radiation (x rays/UV light)
- chemicals that resemble bases - mutations that result in protein structure may be harmful, neutral or beneficial |
How do cells protect themselves from mutations? |
-repair enzymes
-redundancy of the code -some codons code for the same amino acids -only 20 amino acids q |
Cell Division: |
1.) Mitosis- cellular reproduction
2.) Meiosis |
Mitosis |
-important for growth, repair
-ex: fetus -reproduction of single celled organism Function: produce 2 new cells from 1 old cells, (daughter cells) genetically identical to the mother cell |
Meiosis |
-production of sperm and egg cells
-gametes= sperm/eggs -reduces the number of chromosomes in the gametes by half -occurs in the ovaries/testies |
Homologous chromosomes |
-2 chromosomes similar in structure, 1 mom and 1 dad
-contain the same genes in the same location on the chromosomes -each gamete contains a unique mixture of your DNA |
Haploid |
-containing only 1 (gametes) chromosome from each homogolous pair
-sperm cell -different lengths |
Diploid |
containing homologous pairs of chromosomes (all others) |
Gene expression |
-Genes are not active all the time
-different shapes/functions -expressed= transcribed into mRNA and translated into protein |
How is gene expression regulated? |
-1.) turning genes on and off based on the developmental stage of the organism and the type of tissue that the cell is a part of (activator proteins: bind to genes, and then turn them on)
-on: transcription -off: no transcription -2.) varying the rate of transcription or translation |
External environmental cues |
food, sunlight, temperature, behavior
* |
Regulatory Gene |
-a gene that codes for an activator protein
-control expression of other genes by turning them off/on -one regulatory gene may control the expression of many other genes -important during early development |
Cancer |
Uncontrolled cell division or mitosis when a regulatory gene that controls cell division is turned on by mistake, the cell will divide without control
- tumor is malignant |
Oncogene |
a growth regulatory gene that has malfunctioned stimulating uncontrolled cell division, like an accelerator in a car |
Tumor |
-any clump of cells, produced through rapid cell division can be either: benign or malignant (spread) |
Suppressor Gene |
suppressor gene: a gene that inhibits cell division. Mutations prevent inhibition, like brakes
-Mutations: loss of brakes - most cancers require multiple mutations |
Characteristics of Cancer |
rapid cell division and loss of cell differentiation (specialization) |
Metastasis |
-cancer spreads to other parts of the body and changes in cell shape |
What causes Cancer? |
carcinogens, high energy radiations, chemicals that mimic bases, viruses that can insert oncogenes into the DNA of a cell, hormones, certain foods?, tobacco |