Microbio Exam 3

What is a gene?

a piece of DNA that codes for a single protein

What is a genome?

the complete set of genetic instructions for any organism

What is a chromosome?

organized structure that contains most DNA of an organism

What is the genetic code?

What is genetics?

study of how DNA is inherited and how small differences in DNA sequence leads to differences in individuals

What is a genotype?

genetic makeup of an organism

What is a phenotype?

physical properties of an individual

What does the “one gene - one polypeptide” hypothesis mean?

the idea that each gene is responsible for making a single polypeptide

What are the similarities and differences between DNA and RNA?

DNA

- A,C,G,T bases

- deoxyribose sugar

- double-stranded helix

- located in the nucleus

- hereditary molecule (master code) that codes for proteins

RNA

- A,C,G,U bases

- ribose sugar

- usually single stranded

- acts as genetic material and an enzyme

- less stable than DNA (not the best to code genes long-term)

What roles do mRNA, tRNA, and rRNA play in protein synthesis?

mRNA - moves the message from the nucleus to the ribosome

tRNA - transfers correct amino acids to the ribosome

rRNA- makes up the ribosome structure along with protein

What is transcription and translation? (describe and explain what is meant by it)

transcription - DNA is copied into RNA by RNA polymerase in the nucleus

translation - mRNA is decoded in order to make a polypeptide chain by the ribosome in the cytoplasm

Where and how does transcription occur in eukaryotic cells?

in the nucleus, RNA polymerase unwinds and pulls apart the 2 DNA strands and uses 1 to make an RNA copy of the DNA (nucleotides are added one at a time in the right order using the one complementary to the DNA)

When and how does translation occur in eukaryotic cells?

in the cytoplasm/ribosome, mRNA is decoded into a polypeptide chain and the info carried by mRNA is used to make a protein (requires all 3 RNAs)

What are the 3 steps of RNA processing that occur in eukaryotes after transcription and before translation?

1. splicing - removes introns from RNA, joins exons together so they’re ready for translation

2. addition of a 5’ cap - allows ribosomal attachment

3. addition of a poly A tail - 150-300 adenines added to end of RNA, prevents degradation

How do you write the mRNA sequence, tRNA anticodons, and sequence of amino acids in an encoded polypeptide when given a DNA sequence and the genetic code?

look at mRNA codons, not tRNA anticodons

Why and how do bacteria regulate their genes?

What are the potential consequences of a mutation in a DNA sequence to the amino acid sequence of the polypeptide formed?

What are the different types of mutations and what causes them? (classify by type)

Silent mutations - when there is a change in a base pair that does not result in a different amino acid (does not affect protein function)

Missense mutations - when a base pair substitution changes the original codon, therefore changing the amino acid in the protein (can have little effect on the protein and its function, or, the protein may not be able to function properly)

Nonsense mutations - when a single base substitution results in a stop codon (can cause a shortened/truncated polypeptide sequence)

Frameshift mutations - deletion or insertion of 1 or 2 bases

What is a mutagen?

chemicals that cause more mutations

What is the purpose of and procedure for the Ames test?

auxotroph is put on a media with no or low histidine, chemical suspected to be mutagen added to media, if plate looks like control plate the chemical is not a mutagen, if plate has many colonies the chemical is a mutagen

What is the difference between bacterial and eukaryotic chromosomes?

bacteria - single, in nucleoid, have plasmids

eukaryotes. - many, in nucleus, no plasmids

What are plasmids and what kind of genes are found on them?

circular DNA molecules that contain non-essential genes

What is the difference between vertical and horizontal gene transfer? (including understanding processes of transformation, conjugation, transduction)

vertical gene transfer - parent cell undergoes binary fission and creates 2 identical daughter cells

horizontal gene transfer - passing plasmids or other DNA from one bacterium to another in the same generation (transformation - picking up DNA from the environment/dead bacteria, conjugation - picking up DNA from another live bacteria, transduction - picking up DNA from a virus)

What are the internal structures of the prokaryotic cell?

nucleioid - where DNA resides in chromosomes

ribosome - mix of proteins and rRNA that joins amino acids together

plasmid - circular DNA molecules that contain non-essential genes

inclusion bodies - non-membrane bound granules, store nutrients

endospores - only gram positive, resistant to unfavorable conditions

What is the life cycle of spore-forming bacteria and what is the difference between the vegetative and endospore phases?

vegetative phase - normal replication

endospore phase - capable of high-resistance and very long-term survival in adverse environmental conditions

What are the parts of the cell envelope and their functions?

cell membrane - innermost, selectively permeable barrier, generates energy

cell wall - middle, maintains cell shape and structure

glycocalyx - outermost, protects bacterium and keeps from drying out, facilitates attachment to surfaces, aides in formation of biofilms

What is the difference between a slime layer and a capsule?

slime layer - unorganized, loosely attached to cell wall

capsule - highly organized, firmly attached to cell wall

What is the difference between Gram-positive and Gram-negative cell walls?

Gram-positive - thick layer of peptidoglycan, techoic acids reinforce cell wall and determine shape, determine whether bacteria is resistant to antibiotics, no outer cell membrane

Gram-negative - thin layer of peptidoglycan, surrounded by outer cell membrane with porins that act like pores, cell wall contains endotoxins

Why are certain bacteria stained by the acid-fast stain instead of Gram stain?

wax in cell wall is resistant to chemical dyes and does not stain well

What are the parts of the flagellum?

basal body - anchored to cell membrane and cell wall

filament - attached to basal body by hook, allows for 360 rotation

What are the arrangements of flagella?

monotrichous - only one flagellum

amphitrichous - flagella extending from either end of the cell

lophotrichous - clusters of flagella that originate at one end of the cell

peritrichous - flagella randomly distributed over the entire surface of the cell

What is the difference between positive and negative chemotaxis?

Taxis - movement of the cell in response to external cues (+ stimuli is a cell moving towards something, - stimuli is a cell moving away from something)

What is the function of the pilus and fimbrae?

Pili - used for DNA transfer and attachment to surfaces

Fimbrae - used for helping bacteria attach to surfaces and other bacteria

Why do cells tend to be small?

volume (metabolic activity) grows faster than surface area (plasma membrane), as size grows, the surface area-to-volume ratio goes down

What are the structure and functions of the major components of prokaryotic cells?

What are the structure and functions of the major components of eukaryotic cells?

cell wall in fungi (chitin) and plants (cellulose), appendages, nucleus, membrane-bound organelles, cytoskeleton

What are the similarities and differences between prokaryotic cells, eukaryotic plant cells, and eukaryotic animal cells?

prokaryotic cell - single large circular chromosome

plant cell - has chloroplasts, cell wall, one large vacuole, leucoplasts

animal cells - many small vacuoles, many small linear chromosomes

What is endocytosis and exocytosis?

exocytosis - releases cellular contents into extracellular space, packages secretion into a vacuole

endocytosis - uptakes material from outside of cell into cell, picked up by a vacuole

What are the differences between phagocytosis and pinocytosis?

phagocytosis - engulfment of other cells or particles (food)

pinocytosis - engulfment of fluid (drink)

What is the endosymbiotic theory regarding the origin of chloroplasts and mitochondria? Explain the evidence that is used to support the theory.

proposes that the ‘ancestors’ of mitochondria and chloroplasts were once free-living bacteria that were engulfed by a nucleated cell