Study Guide Exam 2 Flashcards
Bacteria typically have a single chromosome- what shape is it?
Circular
What is the name give to the complex of DNA and proteins that form a chromosome?
Chromatin
Most cells contain 2 copies of each chromosome, one inherited from the mother and one from the father- what is the name given to the 2 copies of each chromosome?
Homologous Chromosomes
Because the Y and X chromosome are different, as a pair, they are called…
Non-Homologous or Sex Chromosomes
Define a Gene
Carrier of genetic information that codes for a protein of RNA molecule
Is all DNA genes?
No, only about 2% of the human DNA codes for proteins AKA genes
How many genes do humans have?
Around 20,000
How many chromosomes do humans have?
46 Chromosomes or 23 Pairs
What occurs during Interphase?
DNA replication occurs
Where does DNA duplication begin?
It begins at an AT rich origin of replication sequence
What are the ends of a chromosome called?
Telomeres
What occurs during mitosis?
The nucleus and the 23 pairs of replicated chromosomes are divided into daughter cells
When are chromosomes most easily visible?
During the mitotic phase
What specialized DNA sequence allows one copy of each chromosome to be placed into each daughter cell?
Centromere
What are the two classes of proteins that bind to DNA to form chromosomes?
Histones and Non-histone proteins
What is a nucleosome?
DNA wrapped around histone proteins
What can you say about the genes contained on the regions of interphase chromosomes that are more extended than other regions?
Euchromatin is less condensed and contains more transcribed genes that heterochromatin
What happens to one of the two X chromosomes in females?
It becomes inactivated and forms a Barr Body
As a DNA double helix replicates to form two new double helices, each new double helix contains one parental strand and one new strand of DNA. DNA replication is therefore known to be _____ ______
Semi Conservative
Origins of replication are rich in what two bases?
A and T
What is the name of the enzyme that separates the two strands of DNA in the double helix?
DNA Helicase
What do single strand binding proteins do?
Bind to the opened replication fork strands and prevent it from closing
At origins of replication, two replication forks are formed; DNA replication is thus known to be _______
Bidirectional
What is the name of the small molecule that complementarily binds to the DNA to be replicated?
What enzyme synthesizes this molecule?
RNA Primer
RNA Primase
Why does DNA polymerase need this small RNA primer molecule before it can start synthesizing DNA?
DNA polymerase needs to start from a double strand. It needs the 3’ carbon to form the next phosphodiester bond
The leading strand is synthesized _______
Continuously
The lagging strand is synthesized _________
Discontinuously
What are the name of the fragments of DNA that make up the new strand complementary to the lagging strand?
Okazaki Fragments
Name 3 differences between DNA and RNA
DNA uses deoxyribose, RNA uses ribose, DNA is a double helix, RNA is a single strand, DNA uses thymine, RNA uses Uracil
Is all DNA genes?
No, only 2% of human DNA is genes
If we want to make a single strand of mRNA from DNA where would we start? How do we know where to start transcription?
The promoter sequence aids in the finding of the AUG start site
In DNA replication, the double helix was unwound by helicase. What does this job in RNA synthesis?
RNA polymerase opens the transcription bubble
How do we know where transcription should stop?
A termination sequence will denote where it should stop
What three things occur during mRNA processing
1- Splicing of Introns
2- 5’ Methylated guanine cap is added
3- Polyadenylation tail is added
The following is a sequence of DNA. Transcribe this into RNA and then translate it into protein
5’ CCT CTT ACA CGC CGG GCA TTA 3’
RNA- GGA GAA UGU GCG GCC CGU AAU
Protein- GLY GLU CYS ALA ALA ARG AS
What is a codon and where do you find it?
3 nucleotides- in mRNA from a gene coding sequence
What is an anticodon and where do you find it?
The 3 nucleotide sequence complimentary to the codon found on the anticodon loop of tRNA
If the codon Is GGC, what is the anticodon?
CCG
Describe control of gene expression at each step below
DNA -> pre mRNA -> mRNA in nucleus -> mRNA in cytoplasm -> protein -> active protein
1) Controlling when and how often a gene is transcribed
2) Controlling how the transcript is spliced
3) Controlling if the mRNA leaves the nucleus and goes into the cytoplasm or not
4) Controlling which mRNAs are translated
5) Activating or inhibiting the protein function
Is the Lac operon found in prokaryotes or eukaryotes?
Prokaryotes
Gene Lac 1 codes for what protein?
Repressor Protein
Is the repressor protein always present?
Yes
What does the repressor protein do in the absence of lactose?
Binds to the operator sequence and block RNA polymerase access to the promoter
What does the repressor protein do in the presence of lactose?
Lactose is converted to allolactose and binds to the repressor protein
