Biology - Chapter 15 - Genes and How They Work

A ____ is linear stretch of DNA nucleotides that codes for the assembly of amino acids into a polypeptide chain.

___ uses deoxyribose sugar and ___ uses ribose sugar.

___ bases are A, T, G, and C.

___ bases are A, G, C, and U (uracil).

___ consists of two strands of nucleotides twisted together in a double helix.

___ consists of a single strand.

Combines with proteins to form ribosomes upon which polypeptides are assembled. one of the three types of RNA in the nucleus that genes are transcribed into.

Carries the "blueprint" for protein assembly to the ribosome. one of the three types of RNA in the nucleus that genes are transcribed into.

Brings the correct amino acid to the ribosome and pairs up with an MRNA code for that amino acid.

The path from genes to proteins involves two steps:

Molecules of RNA are produced on the DNA templates (patterns for synthesis of a complement) in the nucleus.

RNA molecules shipped from the nucleus to the cytoplasm are then used as templates for polypeptide assembly.

Transcription VS replication: Only one region of one DNA strand is used as a template. RNA polymerase is used instead of DNA polymerase.

1. Initiation: RNA polymerase binds to a promoter region (start site for transcription of DNA); "sense strand". 2. Translocation/Elongation: RNA polymerase moves along to the end of a gene, attaching complementary bases. 3. Termination: Result: An RNA transcript.

RNA transcripts are modified before leaving the nucleus. 1. Noncoding portions (introns) are snipped out, and actual coding regions (exons) are spliced together to produce the mature transcript. 2. The 5' end is capped with a special nucleotide that may serve as a "start" signal for translation 3. A "poly-A tail" of about 100-200 molecules of adenylic acid is added.