Chapter 12 - DNA & RNA Flashcards
Who was Frederick Griffith?
A British scientist who was trying to figure out how bacteria make people sick.
What did Griffith do to answer his question?
He injected mice with 4 different samples of bacteria. When injected separately, neither the heat killed disease causing bacteria nor the live harmless bacteria killed the mice. But when the 2 were combined, it caused fatal pneumonia.
What did Griffith call the process when the heat-killed bacteria had passed its disease causing ability to the harmless strain?
transformation
What did Griffith hypothesize from his experiment?
When the live, harmless bacteria and the heat-killed bacteria were mixed, some factor was transferred from the heat-killed cells into the live cells. That factor must contain info that could change the harmless bacteria into disease-causing ones.
What did Avery and his group discover?
The nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next.
What is a bacteriophage?
a kind of virus that infects bacteria (“bacteria eater”)
What was Hershey and Chase trying to figure out?
Whether genes were made of protein or DNA. by using bacteriophages
What did Hershey and Chase conclude?
the genetic material of the bacteriophage was DNA, not protein
What are nucleotides?
units that make up DNA
What are genes known to do?
1) carry info from 1 gen. to the next
2) put info to work by determining the heritable characteristics of organisms
3) had to be easily copied
What is a nucleotide made of?
a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous (nitrogen-containing) base
What are the nitrogenous bases of DNA?
Adenine, Guanine, Cytosine and Thymine
Who was Erwin Chargaff?
an American biochemist that discovered that the percentages of guanine and cytosine bases are almost equal and the percentages of adenine and thymine bases are almost equal
Who was Rosalind Franklin?
She used X-ray diffraction to get info about the structure of DNA.
What did photo 51 show?
Photo 51 showed that the strands of DNA are twisted around each other like coils of spring (helix). The angle of the X suggests that there are 2 strands in the structure. It also suggests that the nitrogenous bases are near the center of the molecule.
Who were Watson and Crick?
Made a 3D model of DNA based on Franklin’s Photo 51
What is the structure of DNA called? What does it look like?
Double helix; twisted ladder/spiral staircase
What is base pairing? What does it state?
Explained Chargaff’s rules; for every adenine molecule, there had to be exactly one thymine molecule. And for each cytosine molecule, there had to be exactly one guanine molecule.
Eukaryotic chromosomes contain both DNA and protein, tightly packed together to form a substance called what?
chromatin
What are histones?
proteins that DNA is wrapped around
What is a nucleosome?
beadlike structures of DNA and histone molecules
What do nucleosomes do?
fold enormous lengths of DNA into the tiny space available in the cell nucleus
What are replication forks?
sites where separation and replication occur
What happens in DNA replication?
The DNA molecule separates into 2 strands, and then produces 2 new complementary stands following the rules of base pairing. Each strand of the double helix of DNA serves as a template or model for the new strand
What is DNA polymerase?
The principal enzyme involved in DNA replication
What does DNA polymerase do?
Joins individual nucleotides to produce a DNA molecule; it proofreads each new DNA strand helping to maximize the odds that each molecule is a perfect copy of the original
What are the differences of DNA and RNA?
1) the sugar in RNA is ribose while DNA has deoxyribose
2) RNA is generally single-stranded
3) RNA contains uracil in place of thymine
4) RNA is a disposable copy of a segment of DNA
5) DNA is the blueprint
What are messenger RNA (mRNA) ?
RNA molecules that carry copies of protein-making instructions from the DNA to the rest of the cell
What is ribosomal RNA (rRNA) ?
RNA found in ribosomes
What is transfer RNA (tRNA) ?
transfers each amino acid to the ribosome as it is specified by coded messages in mRNA
What enzyme does transcription require?
RNA polymerase
What happens during transcription?
RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA
What are promoters?
Regions of DNA where RNA polymerase binds to
What are introns?
Sequences of nucleotides that are not involved in coding for proteins
What are exons?
the DNA sequences that code for proteins; they are “expressed” in protein synthesis
What is RNA editing?
RNA molecules edit out the introns out of them before they become functional; exons are spliced together; then a cap and tail are added to form the final RNA molecule
What is a codon?
consists of 3 consecutive nucleotides that specify a single amino acid that is to be added to the polypeptide
How many possible codons are there?
64 ; some amino acids can be specified by more than one codon
What is translation?
the decoding of an mRNA message into a polypeptide chain
Where does translation take place?
ribosome
What happens during translation?
the cell uses information from mRNA to produce proteins
What does tRNA have?
anticodons
What does tRNA do in translation?
It brings the amino acid of the specified codon on mRNA as it attaches its anticodon to mRNA
What are mutations?
changes in the genetic material
What are the 2 types of mutations?
Gene and chromosomal
What are gene mutations?
Mutations that produce changes in a single gene
What are chromosomal mutations?
Mutations that produce changes in whole chromosomes
What are point mutations?
A type of gene mutation that involve changes in one or a few nucleotides
What are frameshift mutations?
A type of gene mutation that shift the reading frame of the genetic message (insertion or deletion)
What are the 4 types of chromosomal mutations?
deletions, duplications, inversions, and translocations
What happens in deletion?
loss of all or part of a chromosome
What happens in duplications?
extra copies of parts of a chromosome are made
What happens in inversions?
the direction of parts of chromosomes are reversed
What happens in translocations?
part of one chromosome breaks off and attaches to another
What is polyploidy?
an organism has extra sets of chromosomes (3N or 4N)
What is lac operon?
a group of genes that must be expressed in order for the bacterium (E. Coli) to be able to use the sugar lactose as food
What is an operator?
region where the lac repressor attaches to
How is the lac operon regulated?
A repressor is attached to the operator. RNA polymerase attaches to the promoter. When lactose is present, a lactose molecule attached to the repressor and changes its shape, making it “fall off” the operator. Once the operator is free, RNA polymerase transcribes the lac operon. When lactose is gone, a repressor attaches itself back to the operator and the lac operon is turned off.
How are most eukaryotic genes controlled?
individually with regulatory sequences that are much more complex that those of the lac operon
Why is gene regulation in eukarytoes more complex than in prokaryotes?
Cell specialization requires genetic specialization but all of the cells in a multicellular organism carry the complete genetic code in their nucleus. Therefore, for proper overall function, only a tiny fraction of the available genes needs to be expressed in the appropriate cells of different tissues. Gene regulation makes this specificity possible
Hox genes control what?
Cell specialization
