Chapter 1: genetics Flashcards
DNA has what four nucleotides?
Adenine, thymine, Guanine and cytosine
Adenine can only hydrogen bond with what?
A Thymine
Cytosine can only hydrogen bond with what?
A Guanine
what does it mean when strands are complements?
The sequence of one strand implies the sequence of the other; If the nucleotide on the 5’ end of one strand is a T’ then the nucleotide on the 5’ is A and so on. the sequences are the same just one of 5’ end and other on 3’
What is the first stage of the expression of genetic information?
Transcription; A DNA strand serves as template for the synthesis of a complementary strand of ribonucleic acid (RNA).
What is the second stage of genetic expression?
Translation; Ribosomes enzymatically link together amino acids to form proteins.
The order in which amino acids are linked together is prescribed by what?
By the RNA’s sequence of bases
There are normally how many copies of each chromosome present in every somatic cell?
two (homologous pairs)
The number of unique chromosomes (N) in a somatic cell is what?
is its haploid number
The total number of chromosomes (2N) is what?
Its diploid number
Humans have a haploid number of what? Therefore have a diploid number of what?
haploid number of of 23 therefore humans have a diploid number of 46
cell division of somatic cells is a process called what?
Mitosis
what is the first step of Mitosis?
- Interphase
- Chromosomes not visible as distinct structure
- diploid cells (2N)
What is the second step of Mitosis?
-Prophase
undergoes DNA replication therefore each chromosome is duplicated
-cell is now 4N
-chromatids are now visible
During cell division each chromosome attaches how?
By its centromere to the mitotic spindle such that the members of each duplicate pair line up across the equatiorial plane of the cell
Once the chromosomes are lined up across the equatorial plane of the cell what happens?
The members of each duplicate pair line are then pulled to opposite poles of the dividing cell by the action of the spindle to yield diploid daughter cells that each have the same 2N chromosomes as the parent cell.
during what phase do the chromosomes align along the spindle?
Metaphase
What is the third phase of Mitosis?
- Metaphase
- chromosomes align along spindle by their centromere
- 4N
What is the fourth phase of Mitosis?
- Anaphase
- Single chromatids chromosomes move to opposite poles
- 4N
At what phase do the duplicate pair line of chromosomes move to opposite poles of the now begining to divide cell?
Anaphase
What is the fifth phase of Mitosis?
- Telephase
- Cytokinesis nearly complete
- resulting cells are 2N
Germ cells are formed how?
Meiosis
Meisosis requires how many consecutive divisions?
2
Before the first meiotic division each chromosome does what? What happens to resulting sister chromatids?
each chromosome replicates but the resulting sister chromatids remain attached at their centromere.
What the order of steps of Mitosis?
1) Interphase (2N)
2) Prophase (4N)
3) Metaphase (4N)
4) Anaphase (4N)
5) Telephase (2N)
In Meiosis how many stages of prophase is there?
2: Middle prophase I (4N) and Late prophase I (4N)
In meiosis how many stages of Interphase is there?
1 ; Intephase (2N)
In meiosis how many stages of Metaphase are there?
2: Metaphase I (4N) and Metaphase II (2N)
In meiosis how many stages of Anaphase are there?
2: Anaphase I (4N) and Anaphase II (2N)
In meiosis how many stages of Telophase is there?
1: Telephase II (N)
What are the stages of Meiosis?
1) Interphase (2N)
2) Middle prophase I (4N)
3) Late prophase I (4N)
4) Metaphase I (4N)
5) Anaphase I (4N)
6) Metaphase II (2N)
7) Anaphase II (2N)
8) Telophase II (N)
At what phase of meiosis do the homologous pairs of the doubled chromosomes line up across the equatorial plane of the cell in zipper like fashion?
Metaphase I (4N)
When and how does cross-over occur?
During Metaphase I; the alignment of the doubled chromosomes across the equatorial plane of the cell permits an exchange of the corresponding sections of homologous chromosomes called cross over.
During what phase of meiosis do the spindles move the members of the homologus pair (twin chromatid chromosomes) to the opposite poles of the cell?
Anaphase I (4N)
When does meiotic division occur? what is the result?
Right after Anaphase resulting in a cell containing diploid (2N) chromosomes; also leading to phase metaphase II (2N)
What is the start of the second meiotic division stages?
Metaphase II (2N); sister chromatids still attached by centromere
What happens in Anaphase II?
The sister chromatids separate to form chromosomes and move to opposite poles of the dividing cell.
What happens in telephase II?
Cytokinesis nearly complete resulting in gametes (N)
what are the steps of prokaryotic cell replication via Binary fissiom
1) starts with mother cell with chromosome
2) The cell is elongated and replicates its DNA
3) DNA molecules separate, cross membrane starts forming
4) cross membrane membrane completely forms
5) Daughter cells form
in the case of codominance phenotype does what?
reveals genotype
Give example of co-dominance
a pure red flower is crossed with a pure bred white flower to get a pink flower. when two pink flowers are crossed a ratio of 1:2:1 of red, pink, white flowers are produced.
if two hetero genes are crossed what is the ratio of getting homo dominant: heterozygous and homozygous recessive?
1:2:1
if the red and white flower produce a pink flower what trait(s) are said to be codominant?
red and white are codominant
ABO blood group system is an example of what?
a gene with multiple alleles
The A antigen and B antigenvin blood are what type of traits?
codominant;I^A and I^B
what is chromosomal theory of inheritance?
theory that genes are a part of chromosomes
what are autosomes?
all chromosomes that arent sex chromosomes
If a trait distribution is parallel to that of the X chromosome this shows what?
The Y chromosome does not contain it and thus kt is sex linked; such as the white eye trait of flies
genes that reside on the same chromosome do NOT what?
Do NOT sort independently these are linked genes
The crossover frequency of a pair of linked genes varies directly with what?
their physical separation along the chromosome.
How can it be determined if two recessive traits that affect similar functions are allelic (different forms of the same genes)
Complementation test
what is the complementation test:
used to see of two recessive traits are allelic;the homozygote for one of the traits is crossed with a homozygote for the other. if 2 traits are nonallelic the progeny willchave a wild type phenotype because each homologous chromosome supplies the wild type function the other on lacks.
If you cross a fly with homozygote eye mutation purple with homozygote mutation brown eyes what is the result? what does this indicate?
you get wild type eye phenotype (red eyes) meaning the two traits purple eyes and brown eyes are nonallelic.
If you cross a fly with the homozygote eye mutation white with homozygous coffee eye mutation what is the result? what does this indicate?
you get a non wild type eye color (eyes are not red); indicating the white eye mutationvtrait and coffee eye mutation trait are allelic
individuals with alkaptonuria produce what? why?
Urine that darkens with air exposure as a consequence of the oxidation of homogentistic acid they excrete.
alkaptonuria is what type of disorder?
Recessive metabolic disorder
Why do some individuals have alkaptonuria?
They lack enzyme that metabolizes homogentistic acid
George Beadle and Edward Tatum showed what?
There is a one-one correspondence between a mutation and the lack of a specific enzyme.
a more acurate dictum other than one-one enzyme might be what? Why?
one gene- one polypeptide; because many genes specify proteins that are not enzymes and many proteins consist of several independent subunits.
is One gene-ome polypeptide completely accurate though? why or why not?
No; because RNAs with structurally and functional roles are genetically specified.
