CHapter 4 Genetics and Cellular Function

Gene

Information containing segment of DNA that codes for the production of a molecule of RNA which in most cases goes on to play a role in the synthesis of one or more proteins. The amino acid sequence of a protein is determined by a nucleotide sequence in the DNA.

Function of RNA

Interpret the code in DNA and use those instructions to synthesize proteins. _____ is a disposable molecule that works mainly in the cytoplasm.

Nucleotides

DNA an other nucleic acids are polymers of ______. A ______ consists of a sugar, a phosphate group, and a single0 or double0ringes nitrogenous base.

Chromosomes

46 long filaments of chromatin is called ______.

Base Pairs

A and T, C and G.

Histone

A disc shaped cluster of eight proteins around which a DNA molecule winds for a bit more than 1.5 turns.

Chromatin

A naked double helix of DNA complexed with proteins that together form a filamentous material called _____.

Centromere

A pinched spot where the two sister chromatids are joined.

Kinetochore

A protein plaque on each side of the centromere that has a role in cell division.

Base Triplet

A sequence of 3 DNA nucleotides that stands for 1 amino acid.

Anticodon

A series of three nucleotides complementary to a specific codon of mRNA.

Genetic Code

A system that enables these 4 nucleotides to code for the amino acid sequences of all proteins.

Codon

A three base sequence in mRNA.

Start Codon

AUG. Serves as a code for methionine and as a start codon.

Purines

Adenine and Guanine, double carbon nitrogen rings.

Genome

All the DNA, both coding and noncoding, in one 23 chromosome set.

Deoxyribonucleic acid (DNA)

An acidic, phosphorous rich substance. A self-replicating material present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.

RNA Polymerase

An enzyme that binds to the DNA and assembles the RNA.

Human Genome Project

Carried out from 1990 to 2003, biologists now know the base sequence of more than 99%.

Function of DNA

Carry instructions called genes, for the synthesis of proteins.

Nucleosome

Consists of a core particle (spool of histones with DNA ribbon around them) and a short segment of linker DNA.

Translation

Converts the language of nucleotides into the language of amino acids.

Pyrimidines

Cytosine and Thymine, single carbon nitrogen ring

Ribosomes

Found in the cytosol and on the outside of the RER and nuclear envelope. Inactive ribosomes occur in the cytosol in two pieces- a small subunit and a large subunit. Each is composed of several enzymes and ribosomal RNA (rRNA) molecules. The two subunits come together only when translating mRNA.

Messenger RNA (mRNA)

Made when a gene is activated. A mirror image of the gene. Most mRNA migrates from the nucleus to the cytoplasm, where it serves as a code for assembling amino acids in the right order to make a particular protein.

Sister Chromatids

Only present when a cell is preparing to divide. A chromosome consists of two identical parallel filaments.

Transfer RNA (tRNA)

Small RNA whose job is to bind a free amino acid in the cytosol and deliver it to the ribosome to be added to a growing protein chain. It is a single stranded molecule that turns back and coil on itself to form an angular L shape. One loop contains an anticodon.

Genomic Medicine

The application of our knowledge of the genome to the prediction, diagnosis, and treatment of disease.

Genomics

The comprehensive study of the whole genome and how its genes and noncoding DNA interact to affect the structure and function of the whole organism.

Law of Complementary Base Pairing

The fact that one strand governs the base sequence of the other.

Initiator tRNA

The first tRNA to bind to a ribosome at the start of translation. Always has the anticodon UAC and always carries methionine.

Chromosome Territory

The last state of DNA compaction. A chromosome is packed into its own spheroidal region known as the ______. It is permeated with channels that allow regulatory chemicals to have access to the genes.

Transcription

The process of copying genetic instructions from DNA to mRNA. Occurs in nucleus.

Translation

The step from mRNA to protein. Occurs in cytoplasm.

Stop Codon

UAG, UGA, and UAA. They signal end of message.

Single Nucleotide Polymorphisms

Various combinations of these _______ account for all human genetic variation.

Pre-mRNA

mRNA that contains "sense" portions called exons or "nonsense" portions called introns. The introns are cut out and mRNA is spliced back together and ship out of the nucleus.