Biology Exam #3 Flashcards
What is the purpose of cell division?
FOR MAINTENANCE!
To replace damaged cells,
growth for asexual reproduction (bacteria reproduces by dividing itself in half, humans dont)
What are chromosomes?
Structure that contains most of the cells DNA
What is asexual reproduction? How many partners does it need?
Reproducing by dividing in half
Creating genetically identical off spring (creates clone)
No mate
What kind of cell division is required in sexual reproduction?
Meiosis
What is the purpose of meiosis?
To produce gametes —-> sex cells (egg and sperm)
All animals have the same # of chromosomes T or F?
False chromosome # is specific to each species
Humans have 46
What is chromatin made up of?
Made of DNA and protein
What is the purpose of chromatin?
To condense DNA to fit into the nucleus
DNA wraps around _____ creating _____.
Histones. Nucleosomes
What happens just before a cell divides?
All its chromosomes must be duplicated by DNA replication
- what is a homologous chromosome?
A matching pair of chromosomes carrying genes with the same characteristics (tt, TT)
Are sex cells somatic cells? And why?
No! Somatic cells are all cells except sex cells
What is a diploid?
A pair of somatic cells
What is a haploid?
Gametes (sex cells) single chromosome set
What set of chromosomes determines a persons sex? Where are they located in karyotypes?
Sex chromosomes
Last set in karyotype
XY= male
XX= female
** what are sister chromatids?
Each side of one duplicated chromosome
***What connects sister chromatids?
A centromere
What are the three stages of cell cycle?
- interface
- mitosis
- Cytokinesis
Which part of the cell cycle is the longest?
Interphase
**What are the four stages in order of mitosis?
Prophase, metaphase, anaphase, telophase
PMAT
What are the three stages of interphase? And what occurs during each?
- G1 - Cell growth
- Synthesis - DNA replication and chromosome duplication
- G2 - Cell growth
What does the process of fertilization involves during the human life cycle?
A haploid sperm fuses with a haploid egg
What is the resulting fertilized egg called?
Zygate
What is the purpose of meiosis?
To make haploid gametes
“crossing over” occurs during which prophase of meiosis?
First
- What occurs during anaphase 1 of meiosis?
Homologous chromosomes are separated
*What occurs during anaphase 2 of meiosis?
Sister chromatids separate
- What is the main difference between metaphase in meiosis and mitosis?
In meiosis- Chromosomes line up next to each other
In mitosis- Chromosomes line up on top of each other
*What is an important outcome of meiosis haploid gametes?
Genetic variation
*How does meiosis produce genetic variation? And during which phase do they occur?
Through:
Independent assortment –> Occurs during metaphase one
AND
Crossing over —> Occurs during prophase one
What occurs during crossing-over that produces genetic variation?
Chromosomes line up next to each other randomly
What occurs during independent assortment that produces genetic variation?
Chromosomes line up next to each other randomly
What is “nondisjunction”? When can it occur in meiosis ?
Can occur in meiosis 1 or 2!
Chromosome pairs fail to separate at anaphase, producing gametes with abnormal #s of chromosomes
What does trisomy 21 mean?
In chromosome set #21 there are 3 chromosomes (instead of 2)
A person with trisomy 21 has what condition?
Down syndrome
What are the differences between diploid and haploid cells?
Diploids have 43 chromosomes - 2 per set
Haploid has 23 chromosomes - 1 per set
What type of cells are produced in mitosis and meiosis?
Mitosis - produces diploid cells
Meiosis- produces haploid cells
What is a gene?
A specific sequence of nucleotides in DNA
Define hereditary
The transmission of traits from one generation to the next
What is the study of hereditary card?
Genetics
- what is character?
A heretical feature that varies among individuals
Ex; flower color
Define trait
A variant of a character
Who is the “father of genetics”?
Gregor Mendel
What is stamens?
Email reproductive part of a flower
What is the result of cross-fertilization?
Hybrids
Does cross-fertilization occur in meiosis or mitosis?
Only meiosis because haploid are made
What is an allele?
Alternative versions of jeans
What is homologous?
An organism that has two identical alleles (RR or rr)
What is heterozygous?
An organism that has two different alleles (Rr)
What is the difference between dominant and recessive allele?
Dominant allele: determines organisms appearance
Recessive allele: no noticeable affect is an organisms appearance
An uppercase letter represents…
A dominant allele (R)
A lowercase letter represents
A recessive allele (r)
How many alleles are carried in a sperm and egg? Why?
Only one, due to meiosis
Define locus
A specific location on a gene along a chromosome
Where are genes located?
Specific positions or loci on chromosomes
What is a phenotype?
Physical appearance
Purple flower, head shape
What is a genotype?
Genetic makeup (Heterozygous or homozygous)
How many sets of chromosomes are in gametes question
One
Where does independent assortment happen?
Metaphase one
What is “wild type”?
Traits that are seen most often in nature (not necessarily dominant)
When reading a Pedegree how do you know if there’s a male or female?
Male = [] Female = 0
What is a carrier?
Individuals who have the recessive allele but appear normal
What are the two types of disorders?
Dominant disorder, and recessive disorder
Define incomplete dominance
F1 hybrids have an appearance between the parent phenotype (Parent flowers are red and white. Baby flowers pink)
How many alleles are involved in ABO blood groups?
3
And heterozygous individuals, when to dominant alleles are expressed this is called…
Codominant (ex: AB blood type)
Which sex chromosomes identify male and female?
XY= male XX= Female
What are autosomes?
All chromosomes other than sex chromosome
How many autosomes and chromosomes do humans have?
44 autosomes
46 Chromosomes
A gene located on a sex chromosome is called…
Sex linked genes
Where are sex linked genes located?
On X chromosome
Does the male or female determine child sex?
Male
The sperm will either be X or Y which fertilize the egg( X)
Every cell in our body has the same DNA? True or false
True
What contains every gene?
All somatic cells
What is gene regulation?
Mechanisms that turn on certain genes while other genes remain turned off
What is gene expression?
The overall process by which genetic information flows from genes to proteins
What is the promoter?
Site where enzyme attaches and initiates transcription
What acts as a switch to turn on/off depending on whether a specific protein is bound there?
The operator
What happens when operator is switch on/off? And what determines the switch?
On= coding for protein
Lactose is present
Off= not coding for protein
Lactose is absent
The operator and promoter are located where on the gene?
Upstream
Promoter operator and genes are in_______?
DNA
What is a repressor? What does it do?
A protein
It finds DNA, binds to operator in DNA gene and blocks access to promoter. Genes aren’t expressed
When lactose binds to repressor protein it becomes _______?
Inactive
Lactose is a________ to the gene. Why?
A bodyguard!
When present it fights off repressor so it won’t block expression
Where does X chromosome inactivation occur?
In female mammals
How does DNA allow proteins in?
By Decondensing them
What is the most important stage for regulating gene expression?
Transcription initiation
What does the DNA protein assembly promote?
The binding of RNA polymerase to promoters
What do enhancers do?
Control the DNA sequence
What do enhancers bind to?
Two types of proteins called transcription factors
What do silencers bind to?
Proteins called repressors
Housekeeping genes are important for _____.
Respiration
