BIOL 300 - Chapter 1

what is the central dogma?

DNA to RNA to Proteins

what is genetics?

study of the genome (all genetic info within an organism)

what are genes?

DNA sequence that specifies one or more RNA related sequence (non coding or coding)

where do genomes live?

cytoplasm (bacteria), nucleus, mitochondria, chloroplast (plant)

what is the packaging form for eukaryotic genomes?

chromosomes

what is the packaging form for prokaryotic genomes?

plasmid

what percent of our genome contains genes and encodes proteins?

1%

what is diploid?

two copies of chromosomes, inherited maternally and paternally

what is monoploid?

one copy of chromosome

what is polyploidy?

multiple (3+) copies of chromosomes

what is a homologous chromosome?

matched pairs of chromosomes in a diploid organism that share the same length, centromere position, and carry the same genes in the same order

what are traits?

observable and measurable characteristics

what is a simple trait?

one gene encodes for one trait

what is a complex trait?

several genes encode for one trait

what is a pleiotropic trait?

one gene encodes for multiple traits

what’s a phenotype?

how a certain trait looks like - observable characteristic

what’s a genotype?

organism’s unique set of genes

what determines traits?

genome and environment - nature AND nuture

what is an allele?

different version of the same gene that carries specific mutations

what can cause DNA mutations?

mutagens (UV, chemicals), replication errors

what did Gregor Mendel do?

first scientist to experiment with the idea of alleles

what is the law of segregation?

the two alleles for a single gene separate from each other during gamete formation, ensuring each gamete receives only one allele.

what is the law of independent assortment?

alleles for different genes (located on different chromosomes) sort independently of one another, meaning the inheritance of one gene's alleles does not influence the inheritance of alleles for a different gene

what is a wild type allele?

“normal” allele

what is a gain of function allele?

turns up the activity of one gene - either more production (not good), gene works better, or new co factors allow for gene to work more efficiently

what is the loss of function allele?

slows down the activity of one gene - partial loss of function or complete loss of function, leads to less or no activity

what is a nucleoside?

nitrogenous base and sugar

what is a nucleotide?

nitrogenous base, sugar, and phosphate group

how many rings do pyrimidines have?

one

how many rings do purines have?

two

what properties does the backbone of DNA have?

hydrophilic, negatively charged but neutralized by positively charged particle so r basic proteins

what properties do the bases of DNA have (the inside part, protected by the backbone)?

hydrophobic, neutral charge

what are the three possible DNA confirmations?

A, B (most common), Z (left handed)

how big is the major groove of DNA?

2.2nm

how big is the minor groove of DNA?

1.2 nm

what do nucleases do?

enzymes that break down nucleic acids by cleaving phosphodiester bonds

where do endonucleases attach?

in the middle - internal bonds

where do exonucleases attach?

onto the ends

what is a nucleotide transition?

mutation that swaps a purine with another purine, pyrimidine with a pyrimidine (so G would replace an A etc)

what is a nucleotide transversion?

mutation that swaps a purine with a pyrimidine, etc (so G would be swapped with C, etc)

what is supercoiling?

DNA’s double helix winds around iself to change the DNAs topology - happens when DNA has no free ends

what is positive supercoiling?

DNA is twisted around itself in the same direction as the two helix strands - clockwise

what is negative supercoiling?

DNA twists around itself opposite as the two strands in helix - counterclockwise

what is the solution to supercoiling?

introduce a transient nick in single stranded region to allow the nicked strand to rotate around the intact one

what is a linking number?

number of times a strand crosses over another in space

what is a writhing number (W) in linkage?

represents turning of axis of the duplex in space

what is a twisting number (T) in linkage?

represents rotation of one strand around the other

what is the first piece of evidence that watson and crick used for the double-helix model?

rosalind franklins diffraction data - shows B-form of helix makes a turn every 3.4 nm and there’s 0.34nm between nucleotides, so there’s 10 nucleotides per turn

what is the second piece of evidence that watson and crick used for the double-helix model?

dna density - helix must have 2 polynucleotide chains and the constant diameter suggest bases that face inward

what is the third piece of evidence that watson and crick used for the double-helix model?

chargaff data - saw proportion of G is same as C, respective with A and T. also noted that composition of DNA can be desribed by G-C sum

how many bonds does G have with C?

3

how many bonds does A have with T?

2

what does DNA being overwound mean?

has more base pairs per turn

what does DNA being underwound mean?

has less base pairs per turn

what is semiconservative replication?

double-stranded DNA splits into template strands and serves as template for synthesis of new daughter strand

what is denaturation?

separation of parental duplex (strands) - usually with heat

what is renaturation?

daughter duplex is reformed in a specific sequential manner

what is the melting temperature in mammals on average?

87C

what determines melting temperature?

length of DNA and G/C content

what is annealing?

when renaturation occurs between complementary nucleic acid sequences

what is a spontaneous mutation?

mutation that occurs due to normal cellular operations at random intervals with environment - could be at base pair, gene, or chromosome level

what is an induced mutation?

mutations caused by mutagens

what is a frameshift mutation?

insertion/deletion of gene sequence due to acridines

what is a nucleotide insertion?

one or more nucleotides is added in a sequence

what is a nucleotide deletion?

one or more nucleotides is deleted in a sequence

what is a forward mutation?

mutations that inactivate a gene

what is a back mutation?

mutation that reverses the effects of a forward mutation

what is a silent mutation?

mutation that results in the same amino acid - usually occurs on the 3rd base

what is a missense mutation?

mutation that results in a different amino acid

what is a nonsense mutation?

mutation that results in a early stop codon, leading to proteins that are unstable or inactive

what is an inversion on a chromosome?

pieces of DNA are flipped around and reinserted

what is a translocation on a chromosome?

two chromosomes switch the same part of their chromosome with each other

what is a cis-acting mutaiton?

genetic change in regulatory DNA sequence that affects expression of genes on the SAME chromosome

what is a trans-acting mutation?

change in DNA sequence that affects expression of genes located on DIFFERENT chromosomes or on the same but much further down the chromosome