Medical Cell Biology and Genetics (MCBG) Flashcards
What is heterochromatin and does it show as light or dark in em?
DNA stored as solenoids.
Dark.
What is euchromatin and does it show up as light or dark in em?
DNA stored as beads on a string.
Light.
Are euchromatin or heterochromatin genes expressed?
Euchromatin
What is the limit of resolution?
The minimum distance at which two objects can be distinguished.
How do prokaryotic cells differ from eukaryotic cells?
Prokaryotes have no nucleus, they have a cell wall and no membrane bound organelles (all biochemical processes occur in the same compartment).
What are the parts of a phospholipid?
Hydrophilic head- choline, phosphate, glycerol
Hydrophobic tail- 2 fatty acids
What does amphipathic man?
Both hydrophilic and hydrophobic
What is the glycocalyx?
Cell sugar coat on outside of plasma membrane
What is the fluid mosaic model?
Phospholipid bilayer
Proteins embedded in the bilayer
What are the functions of the plasmalemma?
Selective permeability Transport of materials along cell surface Endo/exocytosis Intercellular adhesion/recognition Signal transduction
Function of RER
Protein synthesis
Function of SER
Lipid synthesis and transport
Ovary/testis/adrenal gland- steroidogenesis
Where is the destination of the product of free ribosomes and ribosomes on the RER?
Free-cytoplasm
RER-for export
Which sides are the cis and trans faces of the Golgi body?
Cis-side closest to RER
Trans-opposite side
Functions of Golgi body?
Modify, sort , concentrate and package proteins into vesicles
What are the types of secretion?
Signal-mediated diversion to lysosomes
Constitutive secretion
Signal-mediated diversion to secretory vesicles for regulated secretion
What is the difference between primary and secondary lysosomes?
Secondary lysosomes have already fused with a bacterium and broken it down. Bacterial matter is left inside.
What makes lysosomes?
Golgi apparatus
What do lysosomes do?
Fuse with material requiring digestion
What do peroxisomes do?
Detoxify molecules in the liver/kidney including alcohol, phenols, formed acid and formaldehyde
How often do mitochondria divide?
Every time the cell divides
How are actin microfilaments distributed in the cell?
Around the edge and in microvilli
How are intermediate filaments distributed in the cell?
Evenly around the cell (not microvilli)
How are microtubules distributed in the cell?
Branching out from nucleus (not microvilli)
How are microtubules arranged in a cilium/flagellum?
9+2 arrangement
What type of helix is DNA?
Right-handed alpha helix
What is the major groove?
Large gap in side of helix
How is DNA packaged?
DNA is wrapped around histones with linker DNA connecting each of these. 8 histones make up one nucleosome. These beads on a string are then packaged into solenoids.
What are genes?
They carry the code for proteins
What is the genome?
Entire DNA sequence
What is a nucleoside?
Base and sugar
What is a nucleotide?
Base, sugar and phosphate
What is the difference between ribose and 2-deoxyribose?
There is no O on the second carbon
Why is DNA negatively charged?
The phosphate group is negatively charged
Which bases are purines?
Adenine and guanine
Which bases are pyramidines?
Cytosine, uracil, thymine
What type of polarity does DNA have?
5’ to3’
Why is DNA 5’ to 3’?
A phosphate is bonded to both the 3rd and 5th carbon
How many hydrogen bonds form between G andC?
3
How many bonds form between A and T?
2
What is heterochrimatin and does it show as light or dark in em?
DNA stored as solenoids.
Dark.
What is euchromatin and does it show up as light or dark in em?
DNA stored as beads on a string.
Light.
Are euchromatin or heterochromatin genes expressed?
Euchromatin
What is the limit of resolution?
The minimum distance at which two objects can be distinguished.
How do prokaryotic cells differ from eukaryotic cells?
Prokaryotes have no nucleus, they have a cell membrane and no membrane bound organelles (all biochemical processes occur in the same compartment).
What are the parts of a phospholipid?
Hydrophilic head- choline, phosphate, glycerol
Hydrophobic tail- 2 fatty acids
What does amphipathic man?
Both hydrophilic and hydrophobic
What is the glycocalyx?
Cell sugar coat on outside of plasma membrane
What is the fluid mosaic model?
Phospholipid bilayer
Proteins embedded in the bilayer
What are the functions of the plasmalemma?
Selective permeability Transport of materials along cell surface Endo/exocytosis Intercellular adhesion/recognition Signal transduction
Function of RER
Protein synthesis
Function of SER
Lipid synthesis and transport
Ovary/testis/adrenal gland- steroidogenesis
Where is the destination of the product of free ribosomes and ribosomes on the RER?
Free-cytoplasm
RER-for export
Which sides are the cis and trans faces of the Golgi body?
Cis-side closest to RER
Trans-opposite side
Functions of Golgi body?
Modify, sort , concentrate and package proteins into vesicles
What are the types of secretion?
Signal-mediated diversion to lysosomes
Constitutive secretion
Signal-mediated diversion to secretory vesicles for regulated secretion
What is the difference between primary and secondary lysosomes?
Secondary lysosomes have already fused with a bacterium and broken it down. Bacterial matter is left inside.
What makes lysosomes?
Golgi apparatus
What do lysosomes do?
Fuse with material requiring digestion
What do peroxisomes do?
Detoxify molecules in the liver/kidney including alcohol, phenols, formed acid and formaldehyde
How often do mitochondria divide?
Every time the cell divides
How are actin microfilaments distributed in the cell?
Around the edge and in microvilli
How are intermediate filaments distributed in the cell?
Evenly around the cell (not microvilli)
How are microtubules distributed in the cell?
Branching out from nucleus (not microvilli)
How are microtubules arranged in a cilium/flagellum?
9+2 arrangement
What type of helix is DNA?
Right-handed alpha helix
What is the major groove?
Large gap in side of helix
How is DNA packaged?
DNA is wrapped around histones with linker DNA connecting each of these. 8 histones make up one nucleosome. These beads on a string are then packaged into solenoids.
What are genes?
They carry the code for proteins
What is the genome?
Entire DNA sequence
What is a nucleoside?
Base and sugar
What is a nucleotide?
Base, sugar and phosphate
What is the difference between ribose and 2-deoxyribose?
There is no O on the second carbon
Why is DNA negatively charged?
The phosphate group is negatively charged
Which bases are purines?
Adenine and guanine
Which bases are pyramidines?
Cytosine, uracil, thymine
What type of polarity does DNA have?
5’ to3’
Why is DNA 5’ to 3’?
A phosphate is bonded to both the 3rd and 5th carbon
How many hydrogen bonds form between G andC?
3
How many bonds form between A and T?
2
How is DNA replicated?
Initiation:
DNA polymerase binds to 3’ end of DNA after recognition of origin of replication. A kick-start by primate is required
Elongation:
Helicase unwinds double helix
Replication forks move
The DNA polymerase works in the 3’ to 5’ direction, making a new strand from 5’ to 3’. On the lagging strand this causes Okazaki fragments to form. DNA ligase joins these Okazaki fragments.
Termination:
Occurs when two replication forks meet and DNA ligase joins final fragments
In which phase of the cell cycle does DNA replication occur?
S phase of interphase
Which is the p arm on a chromosome?
The short arm
What are telomeres?
Repeated sequences at the end of a chromosome
Where can centromeres be positioned in a chromosome?
Metacentric (middle)
Submetacentric (between middle and end)
Arocentric (near end)
Telocentric (at end-not in humans)
Explain mitosis
Prophase-nuclear membrane breaks down, spindle fibres appear, chromosomes condense
Prometaohase-microtubles connect to kinetochore spindle fibre, chromosomes condense
Metaphase-chromosomes line up at metaphase plate
Anaphase-centromeres divide and spindles pull sister chromatids apart
Telophase-spindles disappear, nuclear membrane reforms, chromosomes decondense
Cytokinesis-cytoplasm divides
2 identical cells
Explain meiosis
Meiosis 1- same as mitosis 1 but no prometaphase and homologous pairs (tetrad) pulled apart
Meiosis 2-sister chromatids pulled apart
4 haploid cells
What causes genetic diversity in meiosis?
Random assortment of chromosomes (metaphase)
Recombination/crossing over at a chiasma (prophase 1)
What is nondisjunction?
When a centromere fails to split in anaphase
How do you karyotype?
Chromosome number,sex complement,structural changes
What is aneuploidy?
Abnormal number of chromosomes
What does non-disjunction cause?
Aneuploidy
What is mosaicism?
Presence of two or more cell lines in an individual, degree of mosaicism depends on when mistake occurs
What are some functions of proteins?
Catalysts Transporters Structural support Immune protection Ion channels Receptors
What determines the 3D structure of proteins?
Sequence of amino acids
What are amino acids’ structure?
NH2, COOH, H, R groups around a central carbon atom
What is an amino acid residue?
What remains of an amino acid after it has been joined by a peptide bond to form a protein.
How can amino acids be classified?
Hydrophilic/phobic Polar/non-polar Acidic Basic Neutral Aliphatic/aromatic
What bonds are involved in the primary structure of proteins?
Covalent
What bonds are involved in the secondary structure of proteins?
Hydrogen bonds
What bonds are involved in the tertiary structure of proteins?
Disulphide, Ionic, hydrogen, van der waals, hydrophobic
What bonds are involved in the quaternary structure of proteins?
Disulphide, ionic, hydrogen, hydrophobic, van dear waals
Which amino acids are disulphide bonds formed between?
Cytosine residues
What do electrostatic interactions occur between?
Charged groups
What is hydrophobic effect?
Interaction between hydrophobic side chains. Hydrophobic molecules will come together so less of their surface is exposed to water.
What is a normally folded protein in?
Native conformation
How do proteins fold?
The folding process is ordered. Each step involves localised folding with stable conformations maintained.
Driven by need to find most stable conformation.
What are amyloid fibres?
Misfolded, insoluble form of a normally soluble protein
What is the genotype?
Genetic makeup of a person
What is the phenotype?
The physical characteristics a person has
What does hemizygous mean?
Only one allele of a gene on the X chromosome (males)
What happens if a disease is autosomal recessive?
Heterozygotes are not affected
Males and females are equally affected
2 heterozygotes have 25% chance of having affected offspring
2 homozygous recessive people will have affected children
Disease can skip generations
What happens if a disease is autosomal dominant?
Heterozygotes are affected (rare to be homozygous dominant)
Males and females are equally affected
Affected individuals have a 50% chance of having affected offspring
Affected individuals have at least one affected parent
Does not skip generations
What happens if a disease is x linked recessive?
Hemizygous males and homozygous females affected
More common in males
Female carriers have a 50% chance of having affected sons
Affected males cannot give trait to sons
Affected males have at least a carrier mother
Affected females have an affected father and carrier mother
Daughters of affected males are at least heterozygous
What happens if a disease is x linked dominant?
Hemizygous males and heterozygous females affected
Heterozygous females have 50% chance of having affected offspring
Affected males cannot give trait to sons but give it to all their daughters
What are linked genes?
Genes on the same chromosome
What is the genotype?
Genetic makeup of a person
What is the phenotype?
The physical characteristics a person has
What does hemizygous mean?
Only one allele of a gene on the X chromosome (males)
What happens if a disease is autosomal recessive?
Heterozygotes are not affected
Males and females are equally affected
2 heterozygotes have 25% chance of having affected offspring
2 homozygous recessive people will have affected children
Disease can skip generations
What happens if a disease is autosomal dominant?
Heterozygotes are affected (rare to be homozygous dominant)
Males and females are equally affected
Affected individuals have a 50% chance of having affected offspring
Affected individuals have at least one affected parent
Does not skip generations
What happens if a disease is x linked recessive?
Hemizygous males and homozygous females affected
More common in males
Female carriers have a 50% chance of having affected sons
Affected males cannot give trait to sons
Affected males have at least a carrier mother
Affected females have an affected father and carrier mother
Daughters of affected males are at least heterozygous
What happens if a disease is x linked dominant?
Hemizygous males and heterozygous females affected
Heterozygous females have 50% chance of having affected offspring
Affected males cannot give trait to sons but give it to all their daughters
What are linked genes?
Genes on the same chromosome
What do linked genes not show?
Independent assortment at meiosis
What happens to recombination frequency as the genes are further apart on a chromosome?
It increases
What are tightly linked genes?
Genes close together on the same chromosomes
What happens in transcription?
Promoter region is recognised
Transcription initiation factors recruit RNA polymerase
RNA polymerase makes RNA in 5’ to 3’ direction
What are the subunits in prokaryotic ribosomes?
50s and 30s
Overall 70s
What are the subunits in eukaryotic ribosomes?
60s and 40s
Overall 80s
How are stem loops created?
Hydrogen bonds are formed between anti-parallel, complementary sequences
Where is the amino acid attached to tRNA?
3’ end
What is the wobble position?
The 5’ base of an anticodon/3’ base of a codon is the wobble position allowing a tRNA species to recognise more than one codon
How are amino acids joined to tRNA?
An amino acid binds to an enzyme using ATP. Then the specific tRNA molecule binds to the enzyme using ATP and the amino acid of joins to the tRNA molecule and is released.
What happens in translation?
A methionine 40s subunit recognises the cap and start codon and binds to it using ATP. The 60s subunit then joins the 40s subunit.
A complementary tRNA molecule binds to the codon using GTP. A peptide is formed between adjacent amino acids and the uncharged tRNA leaves the site and the ribosome moves along the RNA using GTP. This continues until the stop codon is reached and the tRNA leaves the reading site.
What is the p site of a ribosome?
The first reading site
What is the a site of a ribosome?
The second reading site
