Download Proteins and Genes

PROTEINS
Proteins are used by cells to build structures and are used in chemical activities. Enzymes are
proteins that aid in chemical reactions such as digestion and cellular respiration. Proteins are
composed of carbon, hydrogen, and oxygen. They also contain nitrogen and some sulphur.
They help build cell structures. Whenever cells are damaged proteins are manufactured. Cells
also build proteins to help make new cells. Red blood cells are replaced at a rate of one million per
second. Proteins are used to help this process. So, one million cell membranes and organelles per
second and this is just for red blood cells!
Proteins are composed of 20 amino acid building blocks. The order and number of amino acids
determine the type of protein. The sequencing of amino acids is regulated by the genes located on the
chromosomes. The genes are patterns of nucleotides in DNA. The pattern is used to build messenger
RNA (mRNA) during a process called transcription. The mRNA leaves the nucleus of the cell and
attaches to ribosomes in the cytoplasm. There is another type of RNA in the cytoplasm called transfer
RNA (tRNA). Each tRNA is attached to a specific amino acid. The tRNA is brought into position to join
with mRNA on the ribosome. As this takes place, each amino acid is brought into the correct position in
the chain to build a protein. This process is called translation. A small protein may contain only 8 amino
acids. while some of the longer chains may have up to 400 amino acids. A chain of amino acids may
also be referred to as a polypeptide chain.
Proteins are important in our diet. Our bodies can produce 12 of the amino acids. But it cannot
make the other eight and we must eat foods that contain these "essential amino acids". If not it can
lead to protein deficiencies and disease.
NUCLEOTIDE - The basic structural units of nucleic acid. Each unit is composed of a five carbon sugar, a
phosphate, and nitrogen base.
TRANSCRIPTION - The process by which an mRNA molecule is built using the sequence of nucleotides in
DNA as a template.
TRANSLATION -The process by which polypeptides(proteins) are produced at the ribosome. Transfer
tRNA positions amino acids according to the sequence of nucleotides in mRNA.
POLYPEPTIDE - A chain of amino acids held together by peptide bonds.
GENES
Genes are sections of chromosomes, each of which contains one set of instructions.
Alleles - Two or more alternate forms of a gene. The alleles are located at the same position
(locus) on one pair of homologous chromosomes.
DOMINANT - Alleles of this type determine the expression of the genetic trait in offspring.
Usually expressed with a capital letter. EX: Brown eye colour is dominant over blue eye colour.
The allele for Brown eye colour is represented by a capital B. Blue eye colour would be
represented by a small case b.
RECESSIVE - alleles of this type are overruled by dominant alleles. Which determine the genetic
trait.
GENOTYPE - The alleles an organisms contains for a particular trait. One allele or each trait is
inherited from each parent. Since the alleles occur in pairs, various combinations can occur.
PHENOTYPE - Refers to the observable traits of an individual.
HOMOZYGOUS - Is the term used to describe the genotype of an organism that contains two
alleles that are the same. example; brown eyes are dominant and the alleles would be BB.
Blue eyes are recessive and the alleles would be bb.
HETEROZYGOUS - is the term used to describe the genotype of an organism that contains two
different alleles. Example Bb
PUNNETT SQUARES - a chart used by geneticists to show the possible combinations of alleles in
offspring.
CHROMOSOMAL THEORY
A) Chromosomes carry genes, the units of heredity.
B) each chromosome carries many different genes.
C) Paired chromosomes segregate during meiosis. Each sex cell or gamete(23 chromosomes n
a human) has half the number of chromosomes found in the somatic cells (46 chromosomes
in a regular human cell). This explains why each gamete has only one of the each paired
alleles.
D) Chromosomes assort independently during meiosis. This means that each gamete receives
one member from each pair of chromosomes, and that each chromosome pair has no
influence on the movement of any other chromosome pair.
Females have two X chromosomes, while males have one X and one Y chromosome.
Pathogen - a disease causing organism.