Chapter 9: Genes and Replication Flashcards
What is DNA?
A nucleic acid found in nearly all cells of every living organism on Earth
Unique blueprint to individual, except what?
Clones (identical, not fraternal twins)
DNA is increasingly used in modern society
Paternity tests, criminal investigations, genetic testing and behavior
DNA played a role in
Inheritance, growth, and development raised more questions than answer
DNA structures are a
Double helix, two strands, connected in a twisting ladder structure
The ladder is composed of
Nucleotide units, each containing a sugar molecule, phosphate group, and nitrogen-containing base
Hydrogen bonds form between bases on either side of the ladder in specific pairs
1) A (Adenine) and T (Thymine)
2) G (Guanine) and C (Cytosine)
3) Means DNA always has the same number of C’s and G’s, and A’s and T’s
4) Because of this, we only have to know the sequence of 1 side to translate the other
5) One human DNA molecule can have 200 million base pair (double helix allows it to fit in a cell)
DNA does the blueprint for
How to build and maintain an organism, kept in a code (sequence) of bases
The entire set of DNA is a
Genome
Prokaryotes have
Small, circular DNA
Eukaryotes have
Longer, linear DNA
Broken into short segments called
Chromosomes
The number of chromosomes varies between
Species
Humans have 46 chromosomes (23 pairs), and the percentage of shared.
Genes
Inside a chromosome: Length varies depending upon
Species and particular chromosome
Large chunks are
Non-coding, with interspersed genes: sequence of bases that code for a product (proteins and RNA)
Inside a chromosome not necessarily one version of a gene variation are called, what?
Alleles
Non-coding portion of DNA is called
Junk DNA
Junk DNA can be
Small (10% bacteria) or large (98% human) proportion of DNA
Junk DNA purpose is unclear
1) Found between as well as within genes (introns)
2) Long repeating sequences (nonsense sequences), fragments/duplicates of working genes, non-functional variations
Not all genes are expressed equally in
Cells DNA in each cell codes for everything (in multicellular organism this could be a problem)
Each tissue group only expresses genes necessary for
Its functioning (why we don’t have hair on our stomachs, or acid on our scalps)
Outward expression of trait is
Phenotype
Genetic material present is
Genotype
DNA is copied through
DNA replication such as:
1) Semi-conservative process
2) DNA replication
3) Real time replication
How do we get from DNA to protein?
Transcription and translation
Transcription copying the gene sequence to
Be exported as mRNA (real time)
RNA polymerase (an enzyme) pulls apart a piece of DNA at a
Promoter site and untwists a short segment
RNA polymerase makes an RNA copy of
One strand of DNA putting appropriate base pairs on (no T, instead U (uracil))
Terminate RNA polymerase hits a termination sequence stops
Building RNA, and drops off
In eukaryotes add cap and tail to protect
RNA ends and for recognition; remove introns; export mRNA to cytoplasm
Translation reading of mRNA to
Build proteins
Translation occurs in the cytoplasm and requires:
1) Free amino acids (AA’s) building blocks
2) Ribosomal subunits (builders)
3) Transfer RNA (translator between mRNA and protein languages)
Translation initialize
Ribosome recognizes start codon (sequence of 3 AA’s - AUG) on mRNA and attaches (small and large subunits)
Translation elongate
Find appropriate tRNA to translate; attach AA’s to create a protein
Translation terminate
Ribosome recognizes stop codon, release protein and detach; mRNA can be reused
Mutations are errors or alterations in DNA by
Deleterious, neutral and beneficial
Two classes of mutations
Point and chromosomal mutations
Mutation point
Changing one base pair by replacement, deletions, or insertions, and can cause major downstream problems
Chromosomal mutations
Change to the sequence of genes on a chromosome by deletions, duplications, and inversions
Causes of Mutations
1) Spontaneous
2) Radiation-induced
3) Chemical-induced
Spontaneous
Translation mistake (DNA has a spellcheck function that fixes most of these)
Radiation-induced
High energy can break apart DNA, increasing errors
Chemical-induced
Mutagens: react with DNA to increase the rates of mutation
Results of Mutations: Wrong genetic code =
Bad protein equals to problem
Misspelled gene leads to
Malfunctioning enzyme (can’t do its job)
Mutations often will have
One good copy and one bad copy and still function
