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.