8 DNA and Meiosis

HideShow resource information
  • Created by: Naana
  • Created on: 26-03-15 16:08
What are the three components of DNA?
Deoxyribose sugar, phosphate group and organic base-single ring bases (CYTOSINE and THYMINE) or double ring bases (ADENINE and GUANINE)
1 of 22
How do the components of DNA combine and to give what?
They combine as a result of condensation reactions, to give a single nucleotide (mononucleotide)
2 of 22
How does a dinucleotide form?
When there is a condensation reaction between the deoxyribose sugar on one mononucleotide and the phosphate group of another mononucleotide
3 of 22
What is the structure of DNA?
DNA is made up of two long strands of polynucleotides. The two strands are joined together by hydrogen bonds forming between complementary bases. 3 hydrogen bonds links cytosine and guanine, whereas 2 hydrogen bonds link adenine and thymine
4 of 22
How are the DNA components arranged within the DNA double helix?
DNA structure is like a ladder. Phosphate and deoxyribose molecules form the uprights whereas the organic bases pair together to form steps. The uprights of phosphate and deoxyribose wind around one another to form a double helix
5 of 22
What is the function of DNA?
It is the hereditary material responsible for passing genetic information from cell to cell and generation to generation
6 of 22
How is the DNA molecule adapted to carry out its functions?
Very stable-can pass from generation to generation without change. Two separate stands are joined only by hydrogen bonds, and so can separate during DNA replication and protein synthesis. Very large molecule-carries immense amount of genetic informat
7 of 22
Why is it good that there are base pairs within the helical cylinder of the deoxyribose- phosphate backbone?
The genetic information is to some extent protected from being corrupted by outside chemical and physical forces
8 of 22
What is a gene?
A sequence of DNA bases that determine what polypeptide is made. Polypeptides combine to make proteins so genes determine the proteins of an organism. Genes determine the nature and development of all organisms.
9 of 22
What is a triplet code?
A code that has three bases that is present in DNA. There are 64 codes in total that code for 20 amino acids.
10 of 22
How does DNA in the prokaryotic organism differ from the DNA in eukaryotic organisms?
Prokaryotic cells- DNA molecules are smaller, form a circle and are not associated with protein molecules (no chromosomes present). Eukaryotic cells- DNA molecules are larger, form a line, associate with proteins to form chromosomes
11 of 22
What is a chromosome?
A thread like structure which is made up of protein and DNA. They physically pass on genetic information from one generation to the next
12 of 22
What is the structure of chromosomes?
Chromosomes appear as two threads. Each thread is called a chromatid. The chromatids are joined at the centre point by the centromere
13 of 22
What are homologous chromosomes?
A pair of chromosomes, one maternal and one paternal (not necessarily identical) that determine the same genetic characteristics
14 of 22
What is an allele?
Each gene usually exists in two different forms. Each of these forms is called an allele. Each individual inherits one allele from each parent. If the alleles are different each allele will code for a different polypeptide
15 of 22
Why is meiosis necessary?
To maintain a constant number of chromosomes in the adults of the species. The number of chromosomes are halved in meiosis (23 chromosomes) before the two gametes fuse at sexual reproduction to give full set of chromosomes (46 chromosomes)
16 of 22
How does meiosis create genetic variation?
1) Independent segregation of homologous chromosomes- 23 homologous pairs of chromosomes lay side by side randomly. 2) Recombination of homologous chromosomes by crossing over- the chromatids cross over to produce four cells of different genetic comp
17 of 22
Why are organisms different from one another?
Organisms differ in their alleles. It is the combination of alleles that organisms possess that make species (and individuals within that species) different from each other
18 of 22
What factors increase genetic diversity?
Mutations in the DNA- forming new alleles. Gene flow- this is where different alleles move between populations when individuals migrate from one population migrate into another and reproduce
19 of 22
What is selective breeding (aka selective breeding)?
When you select only individuals with desired characteristics to breed the next generation. Individuals with undesirable characteristics are either killed or prevented from breeding. The variety of alleles is restricted to a small number of desired
20 of 22
What is genetic bottleneck?
When there is an event that causes a big reduction in population e.g. natural disaster so many die. This significantly reduces the number of different alleles in the gene pool (small gene pool). The survivors reproduce and a larger population is crea
21 of 22
What is the founder effect?
This is when just a few individuals start a new colony. These few individuals will only carry small fraction of the alleles of the population as a whole- not very representative. Reduced variety of alleles- smaller gene pool. As a result reduced gen
22 of 22

Other cards in this set

Card 2


How do the components of DNA combine and to give what?


They combine as a result of condensation reactions, to give a single nucleotide (mononucleotide)

Card 3


How does a dinucleotide form?


Preview of the front of card 3

Card 4


What is the structure of DNA?


Preview of the front of card 4

Card 5


How are the DNA components arranged within the DNA double helix?


Preview of the front of card 5
View more cards


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all DNA, genetics and evolution resources »