REVIEW SHEET FOR DNA AND MUTATIONS
TERMS:
Nucleotide- monomers of nucleic acids- makes up DNA- consists of three parts: deoxyribose, phosphate groups, and a nitrogen
base- 4 different kinds
Leading strand- The DNA strand that replicates in the direction that follows the movement of the replication fork (continuous
synthesis occurs)
Lagging strand- the DNA strand that replicates in the direction opposite the movement of the replication fork- DNA forms in
fragments that later are connected by DNA ligase
Antiparallel- The sugar-phosphate backbone of the 2 DNA strands run in opposite directions
Histones- Proteins that bind to DNA and helps to fold DNA into chromatin (human DNA would be 3 ft long if not folded)
Replication fork- The Y shaped region where the 2 DNA strands are separated and replication occurs
Nucleoside triphosphate- A nucleotide that has 2 extra phosphate groups- The energy released from the breaking of a phosphate
bond is used to add the nucleotide to the DNA template strand during replication
Nucleosome- structures that may help to package and fold DNA- structures that may play a role in regulating the way genes are
transcribed
Primase (RNA polymerase)- An enzyme that synthesizes the RNA primer and attaches it to the parent DNA strand (the template)
at the origin of replication
RNA Primer- A sequence of approximately 10 nucleotides that are complementary to the parent DNA- it’s attached at the origin
of replication and allows DNA polymerase to bind to the DNA template strand
Okazaki fragments- the fragments replicated to the lagging strand
Origin of replication- Side where RNA primer is attached and DNA polymerase starts elongation
Semi conservative model- Describes the arrangement of the DNA strands that altar replication (parent/daughter, daughter/parent)
Discontinuous synthesis- way of lagging strand replication- DNA doesn’t replicate continuously- made by Okazaki fragments
Purines- large nitrogen bases- Adenine and Guanine
Pyrimidines- small nitrogen bases- Thymine and Cytosine
Linked Genes- genes on the same chromosome that are inherited together- explains Bateson and Punnett’s results- crossing over
occurred when they aren’t inherited together
Operon-A group of genes that are expressed together because they have related functions
- Ex. 3 lac genes in E. coli code for 3 enzymes that breaks down lactose
Promoter- A region of DNA where RNA polymerase attaches (starting point for transcription)
Repressor- A proteins that prevents RNA polymerase from attaching to the promoter
(prevents transcription)
Operator- Region of DNA where the repressor attaches (found at the end of the promoter and before the genes)
Inducer- A substance that inactivates the repressor- its presence makes it possible for RNA polymerase to attach to the promoter
and transcribe the Operon
Ex. Lactose acts as an inducer that allows the lac Operon to be transcribed (makes repressor fall off operator)
Regulatory Gene- DNA that codes for a protein (Such as a repressor) that controls the expression of other genes
Expressed Gene- When the DNA of a gene is being transcribed (protein synthesis has begun)
Hox gene- A series of genes that control where tissues and organs develop in the various regions of an embryo (developmental
gene)
Oncogenes (and proto-oncogenes)Tumor-suppressing genes (and example)AngiogenesisMonoclonal antibodiesCONCEPTS
Process of DNA replication including the roles of the various enzymes
1. The enzyme helicase breaks apart the weak hydrogen bonds that hold the 2 DNA strands together
2. Primase (RNA polymerase) synthesizes the RNA primer and attaches it to the parent DNA strand (the template) at the
origin of replication
3. DNA polymerase adds nucleotides (that are flowing freely in the cytoplasm) to their complementary bases on the parent
strand of DNA
4. DNA ligase connects the fragments of the lagging strand and seals the gaps in the deoxyribose- phosphate backbone
Structure and examples of nucleotides
- Made up of deoxyribose (sugar), phosphate group, and a nitrogen base
- There are 4 different nucleotide, named after the nitrogen base they have:
1. Adenine (A)
2. Thymine (T)
3. Cytosine (C)
4. Guanine (G)
DNA structure and shape
- Consists of 2 strands
- Double helix
- Made up of nucleotides (building blocks)
Compare and contrast different types of chromosomal mutations and gene mutations
Deletion- Piece of a chromosome breaks off and is LOST
Inversion- piece of a chromosome breaks off and reattaches in REVERSE order
Duplication- piece of a chromosome breaks off and is incorporated into a HOMOLOGUS chromosome
Translocation- piece of a chromosome breaks off and attaches to a NONHOMOLOGUS chromosome
Point Mutation- REPLACEMENT of a nucleotide in a gene with a different nucleotide -> because it is a SUBSTITUTION (only
ONE CoDon is affected)
Frameshift Mutation- INSERTION or DELETION of nucleotides into a gene that affects the grouping of CoDons -> can affect
MANY CoDons, (not in multiples of 3)
Map Genes on a Chromosome
1. Identify the Offspring Genotype Frequencies
2. Calculate the Crossover Values Between Genes
3. Map the Genes
Calculate crossover values (and understand relationship to linked genes)
- If the observed phenotypes differ dramatically from the expected phenotypes this implies that genes are linked
Linked genes do not sort independently and therefore you must change your expected phenotypes
Any deviation from the expected results (recombinants) must be due to crossing over (linked genes were
separated)
Crossover Frequency= Total # of Recombinants *100
Total # of offspring
-
- Geneticists compare the number of recombinant offspring (crossing over occurred) to the total number of offspring produced ->
frequency of crossing over between genes on a chromosome is directly related to how far apart they are, therefore crossing over
values can be used as the relative distances on a chromosome map
Morgan and his experiments
- Studied hereditary using fruit flies: easy to raise and maintains, produce many offspring in a short period of time,
4 pairs of chromosomes
- One pair of chromosomes in males have different shapes: XX=girls, XY=boys
- Genes on the same chromosome tend to be inherited together, meaning they’re linked
- Number of recombinants produced can be used to calculate the crossover frequency