Chapter 4 Lecture - Genetics of Cellular Function Flashcards
Give 4 examples of genetic disorders that can impact hereditary traits.
Color blindness, cystic fibrosis, diabetes mellitus, and hemophilia
Define DNA
A long, thread-like molecule with uniform diameter, but varied length
There are ___ DNA molecules (chromosomes) in nucleus of most human cells
46
DNA and other nucleic acids are polymers of ______
nucleotides
Nucleotides consist of what 3 things?
A sugar, phosphate group, and nitrogenous base
Give an example of a type of sugar that can be found in nucleotides
Deoxyribose
What are the two types of nitrogenous bases in nucleic acids?
1) Purines
2) Pyrimidines
What distinguishes purines and pyrimidines from each other?
Purines have a double ring, pyrimidines have a single ring
Which bases are purines and which bases are pyrimidines?
1) Purines - adenine (A) and guanine (G)
2) Pyrimidines - cytosine (C), thymine (T), and uracil (U)
What are the 4 bases found in DNA? What are the 4 bases found in RNA?
DNA bases: A, T, C, G
RNA bases: A, U, C, G
DNA has a ______ _____ shape.
double helix
The nitrogenous bases of DNA are united by ______ bonds
hydrogen
True or false: A purine on one strand always bound to a pyrimidine on the other
True
In DNA, the base A always pairs with ___ and G always pairs with ___
A - T & G - C
A–T has ___ hydrogen bonds
C–G has ___ hydrogen bonds
A–T has two hydrogen bonds
C–G has three hydrogen bonds
What is the law of complementary base pairing?
The idea that one strand determines base sequence of other
Define chromatin
Fine filamentous DNA material complexed with proteins
Define a gene using two different definitions
1) A segment of DNA coding for the synthesis of a specific protein.
2) An information-containing segment of DNA that codes for synthesizing one or more proteins
Define genome
All the genes of one person
Humans have about _____ genes
20,000
Genes only make up ____% of total DNA, the rest is noncoding DNA.
2%
___ interprets the code in ___ to synthesize proteins
RNA interprets the code in DNA to synthesize proteins
RNA functions mainly in the _____
cytoplasm
What are the 3 important types of RNA for protein synthesis?
- Messenger RNA (mRNA)
- Ribosomal RNA (rRNA)
- Transfer RNA (tRNA)
In what 4 ways does RNA differ from DNA?
1) Single stranded (one nucleotide chain not a double helix like DNA)
2) Ribose replaces deoxyribose as the sugar
3) Uracil replaces thymine as a nitrogenous base
4) Functions mainly in cytoplasm
What determines the amino acid sequence of a protein?
The nucleotide sequence in the DNA
The minimum code to symbolize 20 amino acids is ____ nucleotides per amino acid
three
The body can make millions of different proteins based on only ___ amino acids and is encoded by genes made of just ___ nucleotides
The body can make millions of different proteins based on only 20 amino acids and is encoded by genes made of just four nucleotides
Define a base triplet
A sequence of three DNA nucleotides that stands for one amino acid
Define a codon
The 3-base sequence in mRNA
How many codons are there?
64 possible codons available to represent the 20 amino acids.
__ codons code for amino acids; __ are stop codons
61 codons code for amino acids; 3 are stop codons
What are stop codons?
They signal “end of message”
What are start codons?
AUG codes for methionine, and begins the amino acid sequence of the protein
Define transcription
Copying genetic instructions from DNA to mRNA
Define RNA polymerase
An enzyme that binds to DNA and assembles mRNA
How does RNA polymerase assemble mRNA?
1) RNA polymerase reads bases from one strand of DNA
2) Makes corresponding mRNA
What is translation?
The process that converts the language of nucleotides into the language of amino acids
What 3 things participate in the process of translation?
mRNA, tRNA, and ribosomes
Briefly describe the process of translation
1) mRNA carries code from nucleus to cytoplasm
2) Transfer RNA (tRNA) delivers a single amino acid to the ribosome for it to be added to growing protein chain
3) Ribosome adds the amino acid to the protein chain.
_RNA contains an anticodon that are complementary to codon of mRNA
tRNA
Where are ribosomes found and what are they made of?
1) Found free in cytosol, on rough ER, and on nuclear envelope
2) Consist of enzymes and ribosomal RNA (rRNA)
Describe the structure of tRNA
1) One end includes three nucleotides called an anticodon
2) Other end has binding site specific for one amino acid
What are the 3 steps to translation?
Initiation, Elongation,and Termination
Describe the step of initiation (3 parts)
1) Initiator tRNA (bearing methionine) pairs with start codon
2) Ribosome pulls mRNA molecule through it like a ribbon
3) When start codon (AUG) is reached, protein synthesis begins
Describe the step of elongation (6 parts)
1) Next tRNA (with its amino acid) binds to ribosome while its anticodon pairs with next codon of mRNA
2) Peptide bond forms between methionine and second amino acid
3) Ribosome slides to read next codon
4) Next tRNA with appropriate anticodon brings its amino acid to ribosome
5) Another peptide bond forms (between 2nd and 3rd amino acids)
6) Process continually repeats, extending peptide to a protein
Describe the step of termination (3 steps)
1) Ribosome reaches stop codon
2) Finished protein breaks away from ribosome
3) Ribosome dissociates into two subunits
Describe DNA replication (4 steps)
1) DNA unwinds from histones
2) An enzyme unzips a segment of the double helix exposing its nitrogenous bases
3) DNA polymerase builds new DNA strands
4) Newly made DNA wraps around histones
Before a cell divides, it must duplicate its DNA. Why?
So it can give a complete copy of all its genes to each daughter cell
When preparing to divide, the cell makes copy of ____ DNA
nuclear
When preparing to divide, after nucelar DNA is replicated, each chromosome then consists of two parallel filaments of identical DNA called ______
Sister chromatids
Where are chromatids joined?
At the centromere
Define cell cycle
A cell’s life from one division to the next
What are the two main parts of the cell life cycle?
Interphase and mitotic phase
What does interphase of the cell cycle include
1) G1: first gap phase
2) S: synthesis phase
3) G2: second gap phase
What does the mitotic phase of the cell cycle include?
Prophase, Metaphase, Anaphase, Telophase
Describe G1 of interphase
- The first gap phase; the interval between cell birth (from division) and DNA replication
- Cell carries out normal tasks and accumulates materials for next phase
Describe the S stage of interphase
Synthesis phase; the cell replicates all nuclear DNA and duplicates centrioles
Describe G2 of interphase
- The second gap phase; the interval between DNA replication and cell division
- Cell repairs DNA replication errors, grows and synthesizes enzymes that control cell division
Briefly describe the mitotic phase of cell division
The cell replicates its nucleus and pinches in two to form new daughter cells
What is the G0 phase?
Describes cells that have left the cycle and cease dividing for a long time (or permanently)
True or false: Cell cycle duration varies between cell types
True
Define mitosis
Mitosis is cell division resulting in two genetically identical daughter cells
What are the 4 main functions of mitosis?
1) Development of the individual from one fertilized egg to roughly 50 trillion cells
2) Growth of all tissues and organs after birth
3) Replacement of cells that die
4) Repair of damaged tissues
What are the 4 stages of mitosis/ the mitotic phase?
Prophase, metaphase, anaphase, telophase
Describe the prophase stage of mitosis (6 steps)
1) Genetic material condenses into compact chromosomes
2) 46 chromosomes are made of two sister chromatids
3) Nuclear envelope disintegrates
4) Centrioles sprout spindle fibers (long microtubules)
5) Spindle fibers push centriole pairs apart
6) Some spindle fibers attach to kinetochores of centromeres of chromosomes
Describe the metaphase stage of mitosis (2 steps)
- Chromosomes are aligned on cell equator
- Shorter microtubules from centrioles complete an aster which anchors itself to inside of cell membrane
Describe the anaphase stage of mitosis (2 steps)
- Enzyme cleaves two sister chromatids apart at centromere
- Single-stranded daughter chromosomes migrate to each pole of the cell as motor proteins in kinetochores crawl along spindle fibers
Describe the telophase stage of mitosis (5 steps)
- Chromosomes cluster on each side of the cell
- Rough ER makes new nuclear envelope around each cluster
- Chromosomes uncoil to chromatin
- Mitotic spindle disintegrates
- Each nucleus forms nucleoli
Define cytokinesis
The division of cytoplasm into two cells
True or false: Telophase is the end of nuclear division but overlaps cytokinesis
True
Describe the stage of cytokinesis (2 steps)
1) Creates cleavage furrow around the equator of cell
2) Cell eventually pinches in two
Cells replicate under what conditions?
Cells replicate if:
- They have enough cytoplasm for two daughter cells
- They have replicated their DNA
- They have adequate supply of nutrients
- They are stimulated by growth factors (chemical signals)
- Neighboring cells die, opening up space
Cells stop dividing under what conditions?
1) They snugly contact neighboring cells
2) Nutrients or growth factors are withdrawn
3) They undergo contact inhibition—the cessation of cell division in response to contact with other cells
