Exam 3 Flashcards
Why do cells divide?
Asexual reproduction, tissue repair and renewal, development, and growth.
What makes are the resulting cells called after-division
Daughter cells (genetically identical)
What is the main difference between mitosis and meiosis?
Mitosis creates identical copies and meiosis creates non-identical copies
What kind of cells does mitosis occur in?
Stomatic Cells (soma= body)
What kind of cells does meiosis occur in?
Germ cells (reproductive organs, produces gametes)
What is the goal of mitosis?
to create a duplicate cell
What is a genome?
an entire set of DNA in a cell
What is a chromosome?
A structure packed with information in the chromatin that
What is chromatin?
complex of DNA and proteins
What is a ploidy?
the number of copies of chromosomes in genome
How many copies of chromosomes are in haploids, diploids, and triploid?
1,2,3
What is a homozygote?
same alleles on each copy
what is a heterozygote?
different allele on each copy
What is a chromatid?
It is one strand of the duplicated chromosomes (one part of the x shape)
What are each side of chromatid called?
sister chromatids
What is a centromere?
The center of a chromosome that is bonded by a protein.
What is a kinetochore?
a protein that attaches to the sister chromatids to pull them apart.
List the phases of a cell cycle in order.
Interphase, prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis (IPPMATC)
What is interphase?
S: main growth phase
What do prophase and prometaphase do?
prepare for dividing
What do metaphase and anaphase do?
Divide genetic material
What does telophase do?
It reassembles the chromosomes
What does cytokinesis do?
final divide of the cells
What are the two irreversible points of mitosis?
Replication (s-phase), separation of chromatids (anaphase)
Where does mitosis DNA replication occur?
Interphase
What is the goal of mitosis?
to produce two genetically identical daughter cells
What are the three checkpoints of mitosis?
G1: is the cell ready to divide, G2: is the DNA damaged, Spindle: are the chromosomes able to separate properly
Does DNA replication occur during the Mitosis phase?
No: occurs in G2 (interphase)
Why does genetic variation occur?
genetic variation
What is the observable genetic variation called?
Phenotypic variation
What is a gamete?
a specialized cell with half of the chromosomes of the parent cell?
What is a zygote?
cells created by the fusion of two gametes
how are zygotes produced.
One parent cell becomes two daughter cells (gametes) and then the offspring cells are gametes from two different individuals fused together.
Meiosis 1 causes? Meiosis 2 causes?
The parent cell’s homologs separate into daughter cells (xx to x). Then the homologs separate into chromatids into daughter cells (x to I)
What does reduction division mean?
The genetic material is reduced by half because of cell division
What is meiosis simplfied?
Two cycles of mitosis without replication
What are some features unique to Meiosis I?
Cohesion proteins, polar kinetochore, and homologs separate
What are some features unique to Mitosis?
No cohesion between chromatids, the kinetochore is horizontal, and the chromatids are separated.
What is independent assortment?
genes do not prevent other genes from being randomly in DNA (having brown eyes does not make someone more likely to have brown hair)
How does meiosis generate new combinations of genes?
Independent assortment, crossing over, random fertilization
What is crossing over?
genetic recombination between nonsister chromatids that occurs during metaphase I. Parental gene regions are shuffled.
what is Chiasmata?
sites of crossing over
Which portions of chromosomes swap places during crossing over?
The homologous chromosomes swap regions.
What is the Theory of Particulate Inheritance (1866)?
Alleles (particles of inheritance) can be moved around and passed between generations without blending.
What are True-Bred lines?
a group of organisms that will always produce the same phenotype in their offspring even when intercrossed
What are monohybrid crosses?
a cross between only two variations of a single trait.
How do you write a Mendelian ratio?
The ratio will have the dominate number first then the recessive. For example, 3:1 means a 3/4 dominate, 1/4 recessive
What is the law of dominance?
Alleles are dominate or recessive. Dominate alleles will be expressed in the phenotype.
What is the law of Segregation?
Alleles of the same gene will separate into different gammates.
What is a test cross?
Crossing an unknown genotype with a recessive genotype. If heterozygous, the recessive trait has a chance of showing.
What is the law of independent assortment?
Different traits will separate independently from each other (having blonde hair does not influence having brown eyes).
What is a dihybrid cross?
A cross between true-bred parents for two different traits.
What are simple traits?
simple dominant and recessive
What are the complexities of single-gene interactions?
Complex dominance, pleiotropy, multi-alleic genes
What are the complexities of multi-gene interactions
Polygenic traits, epistasis
What is complete dominance?
Dominate alleles masking recessive alleles in the phenotype
What is incomplete dominance?
When both alleles are present in the phenotype? (red + white =pink)
What is codominance?
Both alleles are expressed independently at the same time. ( black cow + white cow = cow with spots)
Do dominant alleles stop recessive alleles?
No: alleles do not interact directly with each other
What is Polygenic Inheritance?
A pattern where a trait is decided by multiple genes. (eyes have 6 genes)
What is Epistasis?
Multiple genes must interact to influence the genotype
What is multifactorial inheritance?
phenotypes are determined by interactions between genetic and environmental factors
What are Mendelian traits?
the inheritance of traits that is controlled by a single gene with two alleles
What is the difference between Pleiotropy and Epistasis?
Pleiotropy has one gene with many traits and epistasis has multiple genes to create one trait.
How are genes carried on?
Chromosomes
What does homogamatic mean?
It is the female sex chromosomes (xx)
What does heterogamatic mean?
It is the male sex chromosomes (xy)
What are autosomes?
Any chromosome that is not a sex chromosome
How any chromosomes do humans have
23: 22 autosomes and 1 sex chromosomes
Do sex chromosomes go through recombination?
No: while they do follow Mendelian laws (separate into different gametes) they don’t recombine (they can be used on punnett squares)
What are sex-linked traits?
Traits determined by genes on the sex chromosomes
What are bar bodies?
Inactivated x chromosomes in a cell (one of the two x chromosomes in females are inactivated randomly)
Why do some genes not follow the expected pattern of chromosomal inheritance?
Recombination and independent assortment
What is the recombination rate based on?
Physical location: the closer traits are on a chromosome together the less likely they will be recombined apart
What are linked genes?
Genes that are close together on a chromosome
What are centimorgans?
a measure of the probability of recombination happening (1 cM + 1% chance of crossing over during meiosis)
What is the maximum recombination frequency?
50%: only two non sister chromatids can cross over from two chromosomes
Can double cross over occur?
Yes but only between one non sister chromatid pair when crossing two chromosomes (the other pair is not effected)
What is the structure of DNA?
5-carbon sugar, phosphate group, nitrogenous base
What is Chargaff’s rule?
Ratios between bases will be equal. [f(A)+f(T)]+[f(G)+f(C)]= 100%
Which nitrogenous bases are purines?
Adenine and Guanine
What does anti-parallel mean?
The strands of DNA run from 5’ to 3’ and connect to each other in a parallel and reversed way
How is the original DNA preserved?
Semi-conservative: one strand is from the original DNA strand and the other is a copy
How does the info in DNA get to the rest of the cell?
DNA stays in the nucleus so DNA is transcribed into RNA then RNA is translated to proteins
What is the difference between transcription and translation?
Transcription is the process of mRNA being created from DNA and translation is RNA-producing proteins in the ribosome
What is the sequence of DNA strands to RNA strands
DNA Coding strand (sense, 5’ to 3’), DNA Template strand (antisense, 3’ to 5’), Transcribed mRNA (5’ to 3’)
What is needed to start transcription
A promoter is needed to start the initiation of RNA (TATA box)
What does RNA polymerase do?
Synthesizes RNA from DNA template strand (5’ to 3’)
How is the process of transcription terminated?
There are specialized sequences to end transcription like AAUAAA and an AAAAA-tail
What are the steps of transcription?
1) Initiation (Promoter region/ RNA polymerase), 2) Elongation (RNA Nucleotides), 3) Termination (AAAA-tail)
What is splicing?
Removing non-coding regions
What are introns?
non-coding regions in a gene sequence that appear in RNA but not in mRNA (they do not make proteins). They also stay within the nucleus
What are exons?
A sequence in genes that code for proteins
What are the differences between exons and introns
Exons are USED to create proteins and introns are REMOVED during RNA splicing
What does the spliceosome do?
Removes introns
Where does transcription occur?
In the nucleus
Where does translation occur?
In the cytoplasm (specifically the ribosome)
Where does transcription occur versus translation
Transcription occurs in the nucleus but translation occurs in the ribosome
Why is it called translation?
RNA is in a different language than proteins (nucleic acids to amino acids)
What is the monomer of proteins?
Amino acids
What is the polymer of proteins
Polypeptides
What are codons?
Triplets of mRNA
What do codons code?
one codon creates one amino acid
What is the reading frame of codons?
The reading frame is an interval of codons that begin and end with the start and stop codons
What is mRNAs job?
To copy the DNA
What is tRNAs job?
add amino acid to polypeptides
What is rRNA’s job?
Assists in the ribosome to catalyze the synthesis of polypeptides
What part of the tRNA attaches to codons
anticodon
What is the enzyme is used to charge tRNA
Aminoacyl-tRNA synthetase
What direction is mRNA fed into the ribosome
5’ to 3’
What are some characteristics of DNA
double helix, complementary bases, antiparallel
What does DNA gyrase do?
It unwinds the DNA ahead of helicase
What does Helicase do?
Unzips the DNA strand
What does SSBP do?
Holds DNA strands apart
What does primase do?
It synthesizes RNA primer for polymerase
What does DNA polymerase do?
Synthesizes new DNA strand
What does Ligase do?
It stitches together Okazaki fragments
What direction does DNA polymerase move in?
5’ to 3’
What are Okazaki fragments?
The lagging strand has Okazaki fragments due to being synthesized in a semi-discontinuous way
What are telomeres?
A cap of repeated sequences at the end of chromosomes that prevents the shorting of chromosomes
What does telomerase do?
It is an enzyme that helps to maintain the length of telomeres preventing ageing
What does exonuclease do?
It removes wrong DNA after DNA is produced (proofreading)
What are point mutations?
When a single nucleotide is changed. This can be caused by substitutions, insertions, or deletions (Ex: ATCGA -> AATCGA)
How do silent point mutations impact amino acids?
no change
What is a missense?
A mutation that causes the amino acid to change
What is a nonsense mutation?
A point mutation that causes a stop codon to occur prematurely
What are the three types of point mutations?
silent, missense, nonsense
What is a frameshift mutation?
Instead of a substitution, a point mutation inserts or deletes
What are triplet mutations?
Three nucleotides at a time are inserted or deleted
What are chromosomal mutations?
A change that alters the structure of a chromosome
What are the types of Chromosomal mutations?
Deletions, duplications, inversions, reciprocal translocations
What are deletion mutations?
When more than three genes are deleted
What are duplication mutations?
If genes gain extra
What are inversion mutations?
Reverse order of codons
What are reciprocal translocation mutations?
A swap gene region between non-homologous chromosomes
