Unit 2: Genetics Flashcards
Structural units that make up DNA:
- two long strands wrapped around each other to form a double helix
- the double helix looks like a twisted ladder, and each strand is composed of many nucleotides
- each strand of DNA composing the double helix has a “backbone” consisting of alternating deoxyribose sugar and phosphate groups
The nitrogen-containing bases are cyclic compounds made up of:
- carbon, hydrogen, oxygen, and nitrogen atoms
The nitrogen-containing bases are named:
- adenine (A)
- thymine (T)
- cytosine (C)
- guanine (G)
- uracil (U)
“A” and “G” are double-ring structures called:
purines
“T”, “C”, and “U” are single-ring structures referred to as:
pyrimidines
Purine A is always paired with:
Pyrimidine T
Purine G is always paired with:
Pyrimidine C
If one strand has the sequence … ATGC …, then the other strand has the sequence:
… TACG …
Structural units that make up RNA:
- second principal kind of nucleic acid
- usually single stranded
- five-carbon sugar in the RNA nucleotide = ribose; which has one more oxygen atom than deoxyribose
One of RNA’s bases is uracil (U) instead of:
thymine
(the other three bases (A, G, C) are the same as DNA
Three major kinds of RNA have been identified in cells; each have a specific role in protein synthesis:
- messenger RNA (mRNA)
- ribosomal RNA (rRNA)
- transfer RNA (tRNA)
type of RNA molecule that directs the incorporation of amino acids into proteins:
mRNA
type of RNA molecule that forms ribosomes:
rRNA
type of RNA molecule that brings amino acids to the ribosomal site where they are incorporated into proteins:
tRNA
- first major step in cell reproduction
- in bacteria, this is followed by the rest of the binary fission process
DNA replication
DNA replication process (simplified):
- DNA double helix is untwisted by special enzymes
- DNA strands are separated from each other and held apart by special enzymes
- new DNA strands are built by DNA polymerase enzymes according to complementary base pairing
- new strands twist with matching old strands to form two complete double helices
allows cells the build cell parts made of protein and enzymes, providing them with unique characteristics / abilities:
Protein Synthesis (Transcription + Translation)
Transcription process (simplified):
- DNA double helix is untwisted at a gene by special enzymes
- DNA strands are separated at a gene and held apart by special enzymes
- RNA Polymerase enzyme uses the DNA template strand as the pattern or guide for building mRNA by complementary base pairing
The newly built mRNA floats away from the gene in the DNA toward a:
ribosome
meanwhile, the two DNA strands are rejoined and twisted back together
permanent change in the base sequence of DNA
- sometimes cause a change in the product encoded by that gene
- ex. when the gene for an enzyme mutates, the enzyme encoded by the gene may become inactive or less active because its amino acid sequence has changed
mutation
the transfer of genetic material form one cell to another involving cell-to-cell contact:
conjugation
Conjugation process (simplified):
- donor is typically F+ (contains a Fertility Plasmid / Conjugation Plasmid)
- recipient is F-
- cell-to-cell contact occurs (by way of a Conjugation Pilus or a Conjugation Bridge)
- a copy of the F factor (the fertility plasmid) is usually transferred into the recipient
