Term
10.2.1
Calculate and predict the genotypic and phenotypic ratio of offspring of dihybrid crosses involving unlinked autosomal genes. |
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Definition
A dihybrid cross is a cross between first generation offspring of two individuals which have two different characteristics. These two characteristics are controled by two genes.
SSbbXssBB
Gives genes Sb Sb and sB sB |
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Term
10.2.2
Distinguish between autosomes and sex chromosomes
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Definition
Sex chromosomes: are the chromosomes that determine your gender, these are X and Y (XX=female, XY=male)
Autosomal chromosomes: All remaining chromosomes which are not sex chromosomes. There are 22 pairs of these in humans. This means there is a total of 23 pairs of chromosomes in humans. (22 autosomal pairs + 1 sex chromosome pair= 23 pairs) |
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Term
10.2.3
Explain how crossing over between non-sister chromatids of a homologous pair in prophase 1 can result in an exchange of alleles. |
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Definition
| A cut is made in one of the chromatids and at the exact point another cut is made in a non-sister chromatid. The two non-sister chromatids join to form the chiasma and crossing over can then occur between the loci of the two genes. When crossing over ends, the combinations of alleles are varied. |
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Term
10.2.4
Define linkage group. |
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Definition
| A linkage group is a group of genes inherited together because they are on the same chromosome. |
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Term
10.2.5
Explain an example of a cross between two linked genes. |
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Definition
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Term
10.2.6
Identify which of the offspring are recombinants in a dihybrid cross involving linked genes. |
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Definition
| Recombinant offspring are offspring that show non parental combinations of alleles, this is opposed to those offspring which show parental combinations, called parental offspring. |
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Term
10.3.2
Explain that polygenic inheritance can contribute to continuous variation using two examples, one of which must be human skin color |
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Definition
Polygenic inheritance is when two or more genes influence the expression of a trait. It is that that most human traits are polygenic. This accounts for the complexity of our inheritance.
Continuous variation: with multiple genes interacting you can get an array of phenotypes. Examples of cont. variation in human traits: skin pigmentation, height, body shape, intelligence. |
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Term
4.4.1
Outline the use of polymerase chain reaction (PCR) to copy and amplify minute quantities of DNA. |
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Definition
| PCR amplifies (makes many copies of) DNA. Ex: if you want to identify a suspect from a small blood sample, you first need to amplify the sample to make lots of DNA for testing. PCR is also used in research any time you need to make DNA from a small sample. PCR only amplifies the segment of DNA you are looking for, not the whole strand. |
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Term
4.4.2
What happens to fragments of DNA gel electrophoresis? |
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Definition
| In gel electrophoresis, fragments of DNA move inan electrical field and are separated according to their size. |
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Term
4.4.3
How is gel electrophoresis of DNA used? |
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Definition
| Gel electrophoresis of DNA is used in DNA profiling. |
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Term
4.4.4
Describe the application of DNA profiling to determine paternity and also in forensic investigations. |
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Definition
| Your DNA profile will be an exact match to any DNA sample from you. DNA profiling steps: 1.) obtain sample of cells and exract DNA. 2.) Use PCR to make many copies. 3.) Digest with restriction enzymes. 4.) Run gel electrophoresis. 5.) Visualize bands on the gel and take a picture. 6.) complare bands to known sample. DNA profiling can be used to determine paternity and also in forensic investigations to get evidence to be used in a court case. |
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Term
4.4.5
Analyze DNA profiles to draw conclusions about paternity or forensic investigations. |
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Definition
| For a suspect look for similarities between the DNA found at the crime scene and the suspect, it should be an exact match. For a paternity test look for similarities betweeen the child and the possible father, it will be a partial match. |
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Term
4.4.6
Outile three outcomes of the sequencing of the complete human genome. |
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Definition
- Study/comparison of humans with other organisms.
- Locating the genes relating to genetic disease -may lead to test to detect carriers.
- May lead to production of pharmaceuticals based on DNA sequence.
- Development of gene therapy -Use the recombinant DNA tech to overcome genetic disease.
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Term
4.4.7
What happens when genes are transferred between species? |
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Definition
| When genes are transfered between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal. |
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Term
4.4.8
Outline a basic technique used for gene transfer involving plasmids, a host cell (bacterium, yeast or other cell), restriction enzymes (endonucleases) and DNA ligase. |
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Definition
| Gene transfer between organisms is done by first cutting out the gene you want from one organism, and then pasting the gene into a vector (means to transfer gene) so that it can be delivered to the other organism. In bacteria and yeast, aplasmid can be used as a vector to transfer a gene. A plasmid is a small, circular DNA strand independent of the organism's own DNA and can be replicated even when the organism isn't going through cell division. The gene is now in the plasmid and the plasmid can be taken up by bacteria/yeast. This is called transformation. The transformed (or genetically modified) bacteria/yeast can now make the protein that the inserted gene specifies. This process is used to make genetically modified E.coli that produce human insulin. They were transformed with the human insulin gene, so they make the human form of insulin. |
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Term
4.4.9
State two examples of the current uses of genetically modified crops or animals. |
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Definition
| Examples: Salt tolerance in tomato plants, synthesis of beta-carotene in rice, herbicide resistance in crop plands and factor 9 (human blood clotting) in sheep milk, GM bacteria produce human insulin and human growth hormone. |
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Term
4.4.10
Discuss the potential benefits and possible harmful effects of one example of genetic modification.
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Definition
Benefits: Improved yeilds, If they produce own pest-control substances, dont need to spray chemicals, can produce rare proteins that are cheaper and produce less pollution than synthesizing the protein in a lab, farmers can be sure what traits they are getting, allow plans to grow in climates around the world (developing nations may benefit from crop opportunities.
Dangers: Possibility of cross-polination with wild plants can introduce new genes into the wild population, genes may be able to cross species, risk of allergies because now the crops are producing new substances, small number of corporations can control crop supply, decrease in biodiversity, if GM crops spread out of designated area, may out compete wild plants for resources. |
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Term
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Definition
| Clone: a group of genetically identical organisms or a group of cells derived from a single parent cell. |
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Term
4.4.12
Outline a technique for cloning using differentiated animal cells. |
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Definition
Animal clones are produced by nuclear transfer.
-Donor differentiated cell
-Unfertilized egg cell has nucleus removed
-Differentiated cell (or nucleus) and enucleated egg are fused.
-Egg now has diploid nucleus
-Egg is prompted to divide by electric pulse
-Embryo can be implanted in surrogate or used in research.
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Term
4.4.13
Discuss the ethical issues of therapeutic cloning in humans. |
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Definition
For:
- Create new tissues for transplant.
- Create compatible transplants if use person's own cells.
- New treatments for genetic diseases.
Against:
- Creating an embryo and it will not go on to be a child.
- Can lead to reproductive cloning.
- Process is not very efficient, only some of the cells will go on to form clones.
- It is tampering with nature.
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