Biology Module 7 Flashcards
Nucleotide
Building blocks of nucleic acids, include sugar (ribose for Rna, deoxyribose for Dna) a nitrogenous base, and phosphate group
DNA double helix
Twisted ladder with twin tails of sugar-phosphate backbones alternating units of deoxyribose + phosphate joined by covalent bonds, two chains are antiparallel
3 prime (3’) or 5 prime
End of nucleic acid terminating at third of fifth carbon of sugar molecule
Base pairs
Adenine (A) Thymine (T) and Guanine (G) Cytosine (C) joined by hydrogen bonds
Purines
Bases with double ring structure (A + G)
Pyrimidines
Bases with single ring (C + T)
Complementary
A pairs with T or U, G pairs with C
Genome
All the genetic info in organism, one circular DNA in bacterial cell, divided among linear chromosomes in Eukaryotic
Gene
Sequence of DNA that encode a specific protein or RNA molecule
Central dogma
Relationship between nucleic acids and proteins as a flow of information
Transcription
Cell produces RNA using DNA as template
Translation
Info in RNA is used to assemble protein
RNA
Intermediate between DNA and protein nucleotides contain sugar ribose as nitrogenous base iris cell, which binds with adenine in complementary base pairs, can be single stranded and catalyze chemical reactions
Messenger RNA
Carrie’s info that specifies a protein divided into genetic codeword codons group of three consecutive MRNA bases that correspond to one amino acid
Ribosomal RNA
Combines of protein to form a ribosome the physical location were translation occurs some help correctly align ribosome others catalyze formation of the bonds between amino acids in developing protein
Transfer RNA
Molecules are connectors that bind an mRNA codon at one end in a specific amino acid, other role is to carry amino acids to ribosome to correct spot along mRNA molecule
Template strand
Contains the DNA sequence that is transcribed to RNA usually two strands
Promoter
DNA sequence that signals a gene start in indicates which strand is the template
Stages of transcription
Initiation: RNA polymerase attaches to promoter and unzipped DNA double helix exposing template strand
Elongation: RNA polymerase moves along DNA template strand in 3-5’ direction adding RNA nucleotides complementary to exposed bases on 3’ end
Termination: DNA signals end of gene upon reaching terminator RNA Pommer enzyme separates from DNA template releases, newly produce RNA, DNA molecule resumes double helix shape
Gene expression
Production of either functional RNA molecule or protein
5’ cap
After transcription, short sequence of modified nucleotides are added to 5’ end of mRNA molecule
Poly A tail
Formed by 100-200 adenine added to 3’ end
Cap + Tail
Enhanced translation by protecting mRNA, from being degraded in cytoplasm and help ribosomes attached to 5’ end of mRNA molecule
Intron
Portions of mRNA that are removed before translation, small, catalytic RNA and proteins remove intron from mRNA.
Exons
Remaining portions that are spliced together to form, mature, mRNA that leaves nucleus to be translated, mRNA have 70+
Genetic code
Set of rules by which a cell uses the codons in mRNA to assemble amino acids into a protein
Codon
A group of free RNA bases corresponding, either to one amino acid, or to a stop signal
First codon
AUG
Stop codons
UGA, UAA, UAG
Anticodon
Found in tRNA freebase loop that is complementary to one mRNA codon
Stages of translation
Initiation: small, ribosomal, subunits bind to 5’ end of mRNA include region of untranslated nucleotides between cap and start codon, which attracts tRNA, carrying amino acid methionine Elongation: tRNA carries second amino acid to second codon where they bind amino acids align and covalent bond is formed peptide bond, release of tRNA ribosomes move down, mRNA by one codon
Termination: ribosome reaches, stop, codon, release factor binds to stop codon release last TRA ribosome units, separate and recycle new polypeptide release proteins that must fold correctly
Operon
Group of related genes, plus a promoter and operator that control the transcription of the entire group at once
Promoter (transcription)
Site which RNA polymerase attaches to begin transcription
Operator
DNA sequence located between promoter and protein and encoding region
Repressor
Protein that when bound to operator prevents transcription of genes
Lac operon
Consist of three genes that code lactose degrading enzyme, promoter and operator
Regulatory tags
Enzymes in cell can modify stretches of DNA by adding or removing the sec consisting of methyl groups
Epigenetics
Study of changes in gene expression that don’t involve changes in DNA sequence
Transcription factors
Proteins that bind DNA at specific sequences that regulate transcription may bind to gene promoter or enhancers
Enhancer
Regulatory DNA sequence that lies outside the promoter may be located near gene or within, but thousands of base pairs away
Signal transduction
Hormone or others binds to outside of cell and trigger series of chemical reactions inside cell mRNA, must exit nucleus and attach to ribosome for protein production
microRNA
Complementary to coding mRNA, when combined silence genes
Mutation
Any change in a cells DNA sequence
Substitution mutation
Replacement of one DNA base with another
Missense mutation
Sub mutation changes a base triplet, so it specifies to different amino acid
Nonsense mutations
Based triplets specifying, amino acid changes into one that encode stop codon, which shorten protein product
Insertion mutation
Adds 1+ nucleotides to a gene
Deletion mutation
Removes nucleotides
Frameshift mutation
Nucleotides are added, or deleted by a number other than multiple of three which disrupts codon reading frame and devastates proteins function
Expanding, repeat, mutation
Number of copies of a free or four nucleotide sequence increases over several generations
Mutagens
Any external agent that includes mutations, such as radiation or pollution?
Transposable element/transposon
DNA sequence that can jump within the genome, if landed ingene can disrupt it
Germ line mutation
DNA sequence changed that occurs in cells that give rise to sperm and eggs, are heritable
Somatic mutation
Occurs in nonsex cells, not heritable
Alleles
Variants of genes, ~25,000 in humans
Homeotic genes
Encode transcription factors that are expressed during the development of an embryo, control formation of organisms body parts
DNA -> transcription-> RNA -> translation
Protein
DNA to RNA letters
AGTC
UCAG
DNA polymerase
responsible for the process of DNA replication, during which a double-stranded DNA molecule is copied into two identical DNA molecules.
