Studied by 9 people
What does DNA stand for?
Deoxyribonucleic Acid
What is the purpose of DNA?
Blueprint for every living thing, genotype
What information does DNA contain?
Information that regulates when, where, and how much of each protein will be made
What is a phenotype and what affects it?
Observable characteristic based on the genotype; also affected by environment
Who established the idea of a gene?
Gregor mendel
What is a gene?
A heritable characteristic; a region of DNA that can be used as a template to produce a final functional product, either a polypeptide or a functional RNA molecule
What is an Allele?
A variation of a gene
What is a dominant trait?
A trait that masks expression of a recessive allele
What is a recessive trait?
A trait that is masked by a dominant allele
What did the Thomas Morgan Group discover?
Through breeding fruit flies, they discovered that genes are located on the chromosome, and they discovered the location of genes on a chromosome.
What is a nucleotide?
DNA is composed of nucleotides
What is a nitrogenous base? How many are there?
Nitrogenous bases are the only varying component of DNA, and there are only 4
What did Erwin Chargaff find out about DNA?
Nitrogenous base composition vaies between species
What are Chargaffs 2 rules?
The base composition of DNA varies between species, and variation depends on the amount of A=T and G=C within a species
Who were Watson and Crick?
Stole image from Rosalind Franklin about DNA and got a nobel prize for discovering helix structure of DNA
Who is Rosalind Franklin?
Used x-ray crystallography to study the molecular structure of DNA, created photo 51
What is significant about photo 51?
Width of a helix can be measured, pitch of a helix can be deduced, helix shows as a consistent spiral, and direction of twisting can be deduced; It proves that DNA was made of two strands that for a double helix.
What did Franklin conclude about the structure of DNA?
There are two outer sugar phosphate backbones with nitrogenous bases paired in the molecules interior, and the backbones are antiparallel
What are the two Purines and is it larger or smaller than the Pyrimidines?
The two purines are A and G and they are larger than pyrimidines
What are the two Pyrimidines and are they larger or smaller than Purines?
The two pyrimidines are C and T and they are smaller than purines
What led to the discovery that purines pair with pyrimidines?
Two purines would be too wide to fit in a DNA helix, and two pyrimidines would be too narrow, but a purine and a pyrimidine would fit properly
What are the four functions of DNA?
Reliably carry heritable information, replicate itself, translate DNA sequence into amino acid/protein sequences, allow for genetic variation by random changes in genetic information (and also a way to limit damage)
What causes DNA to be well protected?
Nitrogenous bases face inwards and are protected by the sugar phosphate backbones, which don’t carry genetic information. The sugar phosphate backbone is flexible, and DNA is held together by hydrogen bonds that can be easily separated, allowing access to genetic information without damaging the strength of the molecule
What is a histone?
Protein that orients, shapes, and packs DNA
What is a Nucleosome?
Tight loop of DNA and Histone
What is heterochromatin?
Tightly packed nucleosomes
What is base pairing?
Two strands of DNA are complementary, so while DNA replicated, daughter strands are build on base pairing rules
What enzyme polymerizes nucleotides?
DNA polymerase
What are the nucleotides that are added to a growing DNA strand called?
Deoxynucleoside triphosphate
What powers DNA replication?
Hydrolysis of phosphates
How does DNA replication begin?
With an RNA primer
What side of a DNA strand can DNA polymerase add nucleotides to?
3’
Why are there leading and lagging strands in DNA replication?
The leading strand can by synthesized continuously, whereas the lagging strand must be synthesized in segments since DNA can only be synthesized in the 5’ to 3’ direction
What are fragments of DNA called on the lagging strand?
Okazaki fragments
How are Okazaki fragments joined together?
DNA ligase
What is the central dogma of biology?
There is a one way flow of information from genes to mRNA and tRNA to the proteins
What is gene expression?
The process by which DNA directs protein synthesis
What are two stages of gene expression?
Transcription from DNA to RNA, and translation from RNA to proteins
What is transcription?
The synthesis of RNA using information in DNA performed by RNA polymerase; typically transcription yields messenger RNA (mRNA)
What is translation?
Synthesis of a polypeptide using information in mRNA, performed by ribosomes
What is the flow of information from a gene to a protein based on?
A triplet code; a series of non-overlapping, three nucleotide sequences
How are nucleotide sequences of a gene transcribed into mRNA and then translated into a chain of amino acids?
A nucleotide sequence of a gene is transcribed into complementary, non-overlapping three-nucletoide sequences of mRNA called codons; these sequences are then translated into a chain of amino acids, forming a polypeptide
Who is George Gamow?
Theoretical physicist who suggested that a 3 letter code must be employed to encode the 20 standard amino acids
How many amino acids are there?
About 20
Codon codes are redundant; What does that mean?
More than one triplet can code for the same amino acid
What is a transgene?
When genes are transplanted from one species to another
What is a mutation and why are they important?
Mutations are changes in stored genetic material, and these changes are the source for genetic variation and are necessary for a species to adapt to a changing environment; some mutations can lead to abnormal proteins that may be nonfunctional or harmful
What are the three types of substitution mutations?
Silent mutations, missense mutations. and nonsense mutations
What are silent mutations?
Changes in a codon that still code for the same amino acid
What are missense mutations?
When the code matches for an amino acid, but not the correct amino acid
What are nonsense mutations?
The stop codon is changed, creating a nonfunctional protein
What are insertions and deletions?
Additions or losses of one or more nucleotide pairs in a gene; these cause frameshift mutations
What is a spontaneous mutation?
A mutation that occurs during DNA replication, recombination, or repair
What is a mutagen?
Physical or chemical agents that increase the rate of mutation directly or indirectly
Which strand is coded for protein?
antisense strand/template strand
How do nucleotides turn into proteins?
DNA → RNA Polymerase → Exons/introns → mRNA → Ribosome → tRNA → Amino Acids → Protein
What are introns and exons?
Exons are coding regions, introns are non-coding regions
What does RNA polymerase do?
attatches to DNA and transcribes DNA to RNA
What does mRNA do?
“Messenger” RNA, made in nucleous and brought to cytoplasm
What do ribosomes do?
Attach to mRNA, translates mRNA to protein
What does tRNA do?
“Transfer” RNA, recognizes mRNA and provides amino acid
What are amino acids used for?
Building block of proteins
What is protein?
series of amino acids that form into a molecule to perform a function
What are the differences/similarities between DNA and RNA?
Same basic components, base, sugar, phosphate; DNA has Thymine, RNA has Uracil; DNA is double stranded, RNA is single stranded; DNA stays in one shape, RNA can fold into multiple shapes and serve many functions
Are all segments of RNA useful?
No
How does transcription and RNA processing occur?
GTP cap is attatched to 5’ end to prevent degredation, poly A tail is attatched to 3’ end as a nuclear export signal
What is a spliceosome?
Cuts out introns and reassembles exons together
Why do introns exist?
Favors multi-domain proteins and rapid new evolution of multi-domain proteins
What is a solitary gene?
A gene only represented once in a haploid gene
What is a duplicated gene?
The same or similar gene represented multiple times in a haploid gene
What do gene families lead to?
Protein families
Why is redundancy important?
Leads to diversity, which can help for tuning a specific function or providing a backup if one part of a cell fails
What is kinesin and what does it do?
A protein that moves objects around cells
What is an example of a redundant gene?
Ribosomal gene structures dispersed in certain cells
What is a karyotype?
Number of chromosomes in the nucleus of a eukaryotic cell
How many pairs of chromosomes does a human have?
23
What is an autosomal chromosome?
Non-sex chromosome
What does diploid and haploid mean?
A diploid cell has two complete sets of chromosomes, whereas haploid cells have half the number of chromosomes (like sex cells)
What are polyploids?
Two or more sets of chromosomes, common in plants
What is the mouse example of gene expression?
The paternal chromosome has dominant brown coat and black eye genes, whereas the maternal chromosome has recessive white coat and pink eye genes. The gene carries the recessive genes despite the dominant genes being expressed
What is a homologous chromosome?
Members of a single pair of chromosomes
What are meiosis and mitosis?
Meiosis is chromosome replication of a sex cell, whereas mitosis is chromosome duplication of a somatic cell
What is mitosis?
Complex process of chromosome duplication
What is a somatic cell?
A non-reproductive cell
What is cytokinesis?
Cell membrane pinches and divides the cytoplasm in half
What are the 4 stages of mitosis?
Prophase, Metaphase, Anaphase, Telophase
What is an easy way to remember the 4 stages of mitosis?
PMAT → Dog pees on a mat
What is prophase?
Chromosomes become visible and centrioles separate and move to opposite poles of a cell
What is prometaphase? (Likely not on test)
Microtubules attatch to end of chromosomes
What is metaphase?
Chromosomes line up across the center of the cell and become connected to the spindle fiber at the centromere
What is anaphase?
Sister chromatids separate into individual chromosomes and are pulled apart
What is telophase?
Chromosomes gather at opposite ends of the cell and lose their distinct rod-like shapes; two new nuclear membranes form around each of the regions
What is interphase?
Phase where cell grows, cell spends majority of time in this phase
What are the stages of cell growth?
Mitotic phase, Interphase G1 (Growth), Interphase S (DNA replicates), Interphase G2 (cell finishes growth)
What is the mitotic spindle?
Separates the cells during cytokinesis
What happens when a mitotic spindle fails?
Cell division can occur to frequently or stop entirely
What is meiosis?
Converts diploid cells into haploid cells; used for sex cells
Why does meiosis create haploid cells?
Sexual fertilization requires two sets of DNA, so sperm and eggs each contain one diploid chromosome
What is the process of meisosis?
Prophase 1, Metaphase 1, Anaphase 1, Telophase 1, Cytokinesis, Interkinesis, Prophase 2, Metaphase 2, Anaphase 2, Telophase 2, Cytokinesis
When does crossing over occur?
Prophase 1
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