Genetics Study guide
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biochemical compounds consisting of one or more polypeptides. A single linear polymer of amino acids bonded together by peptide bonds.
What is the subunit that makes up a polypeptide or protein?
A single linear polymer of amino acids bonded together by peptide bonds.
What kind of bond (specific name) binds amino acids together?
What is an enzyme?
A protein used as a catalyst in reactions or in replication
What is the subunit that makes up each polymer strand?
What are the three components of a nucleotide?
- 1. phosphate group
- 2. nitrogenous base
- 3. pentose sugar
What is the secondary structure of DNA?o
The double helix
What is the specific role of the 1’, 3’ and 5’ carbon in the pentose sugar of a nucleic acid?
- 1’-covalent (phosphodiester?) bond to nitrogenous base 2’-distinguishes DNA and
- 3’-covalent bond to phosphate groupo 5’-covalent bond to
- phosphate group
What kind of bond forms between the 3’ and 5’ carbons of adjacent nucleotides?
Covalent bond to phosphate group
What is the difference between a pyrimidine and a purine?
Pyrimidine- one ring Purine- two rings
What is the basic structure of a nitrogenous base?
a flat planer structure that forms the basis of DNA
Which type of base (pyrimidine or purine) is a
- Purine- Adenine Guanine
- Pyrimidine Thymine (DNA) Uracil (RNA) cytosine
What kinds of bonds form between nitrogenous bases on opposite strands?
How many of these bonds form between a C and a G? Between an A and a T?
What is meant by the “complementarity” of nitrogenous bases?
- Hydrogen bonding is base-specific
- Purine (two rings) to pyrimidine (one
What is meant by “antiparallel” strands of DNA?
One is oriented in the 3’ to 5’ direction, the other is oriented in the 5’ to 3’ direction?
How do the structures of DNA and RNA differ?
Ribose instead of deoxyribose (2’ Carbon has hydroxyl group)
How does a nucleoside differ from a nucleotide?
- Nucleoside = Sugar + Base
- Nucleotide = Sugar + Base + Phosphate
To what carbon is a deoxynucleoside triphospate (dNTP) added in the process of DNA synthesis?
the 3' carbon
How is the dNTP modified as it is added to the growing strand?
The two phosphate groups are cleaved and one becomes the phosphate group of the DNA
why is a there a leading and a lagging strand at each fork? What is meant by discontinuous vs continuous synthesis? What is an Okazaki fragment?
- Dna must be synthesized in a 5 to 3 direction
- o Leading strand (5-3) is continuous
- o Okazaki-bits of DNA between RNA primers
DNA polymerase I-
removes RNA primer replaces it with DNA, an exonuclease
DNA polymerase III-
synthesizes DNA in leading strand and okazaki fragments
breaks hydrogen bonds between two strands of DNA
breaks a covalent bond in the sugar-phosphate backbone of DNA to relieve tension
synthesizes a short polymer of RNA on lagging strand to create okazaki fragments
catalyzes the formation of a covalent bond in the sugar-phosphate backbone of DNA
What is an exonuclease?
An enzyme that removes successive nucleotides from the end of a polynucleotide molecule
Review leading lagging strand diagram
What is indicated by the single black dot on each strand?
The replication origin
DNA polymerase III occurs as a dimer and processes both strands at once. What implications does this have for the configuration of the lagging strand template during synthesis?
Trombone model, or some way to configure it simultaneously
What is the replication origin?
Oric (place on the DNA) in Ecoli
In E. coli, what proteins and sequence elements are involved in initiating the replication bubble?
The initiator protein is dnaA, sequence elements???
What is a replicon?
a length of DNA that is replicated following one initiation event
How many replicons are there in most bacterial chromosomes?
single replicon theta replication in E. coli
How many replicons in eukaryotic chromosomes?
Eukaryotic DNA linear – many replicons??
What molecules maintain the single-stranded configuration of DNA while it is being replicated?
Single-stranded binding proteins
What problems does the lagging strand encounter during DNA replication at the ends of a linear chromosome?
Can’t replicate the last okazaki fragment/last rna primer
What is this region of the chromosome referred to?
What is telomerase and how does it function to solve this problem?
adds nucleotides to 3’ end of lagging strand of DNA as the lagging strand can't quite finish a strand due to last primer issue
What are some suspected roles of telomerase in determining the life span of a cell and in cancer?
- Cell ages as telomeres shorten, eventually cell cannot longer replicate
- Cancer have high telomerase expression so they may be regenerating telomeres Telomerase- protein and RNA, replicates
- telemeres, RNA portion has DNA template
What are the phases of the cell cycle? When are DNA and centrioles replicated?
o G1SG2M. S is replication stage
What is cohesin and what is its function? When and how do cohesin rings disintegrate?
- Protein ring from before DNA replication holds the two copies of the chromosome (two sister chromatids) together throughout the S and G2
- phases. Is broken down by seperase in anaphase 1.
How do meiosis and mitosis differ
- 1) number of cell divisions; Mei-2 Mit-1
- 2) final product;
- Meiosis- 4 different haploid cells
- Mitosis- 2 identical diploid cells
- 3) genetic similarity or differences among daughter cells; Mei-different Mit-identical
- 4) function of the process; Meiosis- produce gametes Mitosis- cell replication
- 5) ploidy levels of cells throughout each process. Mitosis-2n to 2n
- diploid Meiosis-2n to n haploid
How are the following structures used in these
- kinetochore, go to each side of the chromosome and pull centromeres apart
- synaptonemal complex, 3 part structure that develops between synapsed homologous chromosomes
- chiasma, - crossing over occurs here
- centromere- center of chromosome
- centriole- go to each side of the chromosome and pull centromeres apart
- spindle fibers-pull chromatids apart by kinetochore
How do you describe the shape and structure of chromosomes?
Joined chromatids (or one) with a centromere. X
What is a karyotype?
picture of an individual organism's complete set of metaphase chromosomes
What are homologous chromosomes and how can they be identified?
Non identical chromosomes (one from mom and one from dad) that have similar traits. Identified when they line up in meiosis
What are sister chromatids?
Two identical strands joined by a common centromere as a result of a chromosome that duplicated during the S phase of the cell cycle.
What is the difference between a pair of sister chromatids and a pairs of homologous chromosomes?
- Sister chromatids are identical
- Homologous chromosomes- similar but 1 from mommy and 1 from daddy
What is meant by diploid vs. haploid?
- Diploid- 2 copies of each chromosome
- Haploid- 1 copy of each chromosome
At what cell division of meiosis do cells change from diploid to haploid?
What does the “n” value refer to when we say that a cell is 2n or 1n?
Does the value of n change during the process of meiosis or mitosis?
How do the processes of meiosis differ in male and female gamete production in animals?
Male- 4 sperm cells created Female 1 ovum created, polar body useless
go to each side of the chromosome and pull centromeres apart
3 part structure that develops between synapsed homologous chromosomes
crossing over occurs here
center of chromosome
go to each side of the chromosome and pull centromeres apart
pull chromatids apart by kinetochore
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