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OCR 21st Cen Sci. B1

B1

QuestionAnswer
recall that genes are instructions for a cell that describe how to make proteins.
recall that proteins may be [] or [] structural or functional.
An example of a structural protein is collagen and an example of a functional protein is enzymes (e.g. amylase).
Understand that generally characteristics are determined by either genes or enviromental factors or in cases such as weight: both.
Dimples and the ability to roll tongues, genitalia are determined by your genotype.
4 things just caused by genes and not by the environment are natural eye colour, natural hair colour, blood group and inherited diseases.
A scar is an example of a characteristic caused by environmental factors.
Understand that many (most) characteristics are determined by several [] working together genes, an example of this is eye colour.
Differences between individuals of the same species are described as variations. Variation may be due to [], [...] or [] genotype, enviromental factors or both.
The development of different characteristics are controlled by different genes.
Genes occur in long strings called chromosomes, located inside the nucleus of every [] in the organism cell--.
The amount of chromosomes inside each cell is 46, occurring in [] p[]s
Chromosomes are made of molecules of DNA(deoxyribonucleic acid).
Each DNA molecule consists of two strands, which are coiled to form a double helix.
The DNA molecules form a complete set of instructions for how the organism should be c[] constructed and how its individual cells should function.
Genes are sections of very long [] molecules that make up []s in the [] of cells DNA--chromosomes--nuclei--.
Genes control the development of different characteristics by issuing the cells instructions, which it carries out by producing proteins.
Structural proteins are used for cell [] or [] growth or repair.
Enzymes speed up chemical reactions, but are not [...] in the process used up--.
DNA is contained in all o[] organisms, thus it's possible to introduce genetic information from one organism into another organism.
Introducing genetic information from one organism into another produces a new combination of both genes and characteristics. The process is called genetic modification.
Chromosomes normally come in pairs. Both chromosomes in a pair have the same sequence of genes, i.e. the same genes in the same place.
Human cells contiain [] pairs of chromosomes 23--. Sex cells contain on ly [] chromome from each pair 1.
The sex cells are the ova (egg) and sperm.
Sex cells contain single c[] chromosomes.
Chromosomes in a pair carry the same genes in the same place, but there may be different versions of genes called alleles. The two main alleles for eye colour are brown and blue.
For each gene, there are [] alleles 2--. For each gene, an individual inherits one allele per parent. (Which is why individuals can have similarities to both of their parents).
Eye colour and height are just a couple of the characteristics determined by several [] working together genes.
The alleles of each gene can either be the same of different. The process is completely r[] random (thus sibling can have different characteristics).
If alleles are the same, they are homozygous, but if they are different, they are heterozygous.
Alleles can be either [] or r[] dominant or recessive.
If the dominant allele is present on at least one of the chromosomes in a pair, then it will control the develpment of a charasteristic, but a recessive allele can only do so if it is present in both chromosomes (i.e the dominant allele is not present).
Genetic diagrams are used to show all the possible combinations of alleles and outcomes for a particular gene. [#A1,#A2]
With genetic diagrams: capital letters are used for dominant alleles, and recessive alleles are represented with lower-case letters.
It is possible to limit the chances of getting certain diseases and disorders by making changes to your lifestyle.
The 23rd pair of chromosomes determine gender.
In females the sex chromosomes are X and X, and in males, the sex chromosomes are X and Y.
Of the X chromosome and the Y chromosome, the shorter (greatly) is the Y chromosome.
The sex of an individual is determined by an area of the Y chromosome called the [...] ([...]) SRY gene (Sex determing region of the Y chromosome gene).
The sex-determining region of the Y chromosome is called the SRY gene.
If the SRY gene is not present, the embryo will develop into a [], growing [] female, growing ovaries, but if it is present - testes begin to develop.
In the presence of the SRY gene on the Y chromosome, [] begin to develop testes--. After [] weeks, the testes start producing a hormone called []en. 6--androgen--.
With the presence of the SRY gene on the Y chromosome, the testes produce androgen. Androgen is detected by special [] in the developing embryo receptors--, and thereafter, there is growth of male reproductive organs.
Sometimes the Y chromosome is present but androgen is not detected. When that happens, the embryo develops all the [...] except the [] female sex organs except the uterus. The baby is born with a female body, but is infertile.
An organism's genetic makeup (the combination of alleles) is described by the term genotype, and the organism's observable characteristics are described by the term phenotype.
Unlike the large majority, a small number disorders are caused by faulty []es of a single [] alleles--gene-- e.g. [...] and [...] Huntington's Disorder and Cystic Fibrosis.
Huntington's disorder (HD) is a []ic disorder genetic-- that affects the [] n[]ous system central nervous system. (Caused by a faulty gene on the fourth pair of chromosomes).
Symptons of Huntingdon's disease include late on[], tr[], cl[]ess late on set, tremor, clumsiness--. These are in addition to m[] l[]ss, inability to co[]e, m[] changes memory loss, inability to concentrate, mood changes--.
The HD gene damages |cells| in the brain, which causes gradual [], [] and [] changes physical, mental and emotional changes, which develop into continuous [...] and [] involuntary movement and dementia.
The symptons of HD differ from [] to [] person to person, even within the same f[] family.
The initial symptons of HD normally develop in adulthood, which means sufferers may already have had children and passed on the gene.
HD has no c[] cure, so the disorder will eventually lead to premature death.
Everyone who inherits the HD gene will at some point, develop the disorder as the allele that causes HD is dominant (thus only one parent needs to pass on the faulty gene for a child to inherit the disorder).
Cystic fibrosis affects the cell membranes, causing sticky [], especially in the l[], g[] and p[] stick mucus, especially in the lungs, gut and pancreas.
Symptons of cystic fibrosis can include thick m[], difficulty [], chest i[], difficulty in d[] food thick mucus, difficulty breathing, chest infections, difficulty in digesting food.
Cystic fibrosis has no c[] cure.
Is the allele for cystic fibrosis dominant or recessive? The allele for cystic fibrosis is recessive. Therefore, if someone has one recessive allele, they will not have the associated characteristics (of the disorder).
People with one recessive allele are called carriers -- though they may not have the condition/characteristics, they carry the []e and may pass it to their [] allele--children--.
Genetic testing may be used for testing embryo for embryo []ion (i.e. pre-...) embryo selection (i.e pre-implantation genetic diagnosis), predictive testing for [] diseases and testing an individual before [] drugs predictive testing for genetic diseases and testing and individual before prescribing drugs.
{With aminiocentesis testing: a needle is inserted into the [], taking care to avoid the [] uterus, taking care to avoid the fetus and a small sample of [] fluid, which carries cells from the [] is extracted amniotic fluid, which carries cells from the fetus is extracted. [#B1]
{With chrionic Villus Testing: a special catheter is transfered to the placenta. Samples of chorionic [], which are made from [] cells are removed villi, which are made from fetal cells are removed. [#B2]
A True Positive is where the test result says the fetus [...] and the reality is that the fetus [...] has the disorder and the reality is that the fetus has the disorder. A True Negative is where the test result says the fetus [...] and the reality is the fetus [...] the fetus doesn't have the disorder and the reality is that the fetus doesn't have the disorder.
A False Positive is where the test result says that the fetus [...] and the reality is that the fetus [...] has the disorder and the reality is that the fetus doesn't have the disorder. A False Negative is where the test says that the fetus [...] and the reality is that the fetus [...] doesn't have the disorder and the reality is that the fetus has the disorder.
False negatives are rare and false positives are even rarer. However, the consequence of a false positive is that the parents may choose to terminate the pregnancy when the fetus is healthy.
Testing adults and fetuses for alleles that cause genetic disorders has implications that have to be considered, including: risk of mis[] as a result of cell []ling for the genetic test, using results that may not be a[] risk of miscarriage--cell sampling--using results that may not be accurate--. More over, should they have [] at all? Shoud the pregnancy should be []? Should other members of the family should be [] ? children-- terminated-- told--.
It is thought that there is always a difference between what can be done (i.e. what is technically possible) and what should be done.
Genetic testing could be used to create detailed genetic profiles, which could be used to stop the passing on of genetic disorders, eventually eliminating them.
It has been suggested that babies should be screened at birth, allowing doctors to tailor h[]re for the individual and take action to prevent problems before they occur healthcare--.;
One view of testing babies at birth is that it would be a good thing; there would be less s[]ing and [] could be used elsewhere suffering and money could be used elsewhere. Another view is that disorders are [] and it would be wrong to eliminate them natural--.
The storage of genetic information raises questions about c[] confidentality. There are concerns that without tight laws and regulations in place, companies could use the information to d[...] discriminate agaisnt individuals, e.g someone may be turned down for a job or refused insurance because they have a high risk of getting cancer.
Embryo selection is another way of preventing babies from being born with [] [] genetic disorders. Embryos can be produced by [] [] [] in vitro fertilisation.
Genetically testing embryos for embryo selection is called Pre-implantation Genetic Diagnosis (PGD).
With PGD, after fertilisation, the embryos are allowed to divide into [] cells before a single cell is [] from each for another testing 8 cells before a single cell is removed from each for another testing. Generally the cells are tested to see if they carry the alleles for a specific genetic disorder, i.e. the disorder that one of the parents carries or has.
Embryo selection is controversial. Some people disagree with it because they believe it is un[] unnatural. There are also concerns that people could start using this method to select the [] of their baby in advance characteristics [such as eye colour, sex and IQ]--.
If PGD is allowed to happen it could reduce v[] in humans variation--.
Many questions about an issue to do with scientic procedure, such as 'does it work and is it safe?' may be answered with further scientific research.
Bacteria, plants and some animals can reproduce a[] asexually to form clones.
Clones are individuals with identical genes.
Any differences between clones are likely to be due only to environmental factors.
Clones of plants occur naturally when plants produce either bulbs or runners.
Clones of animals occur naturally when the cells of embryos seperate (e.g. i[]l t[]s). identical twins--
Clones of animals may occur artificially when there is a transferring of the [] from an [] body [] nucleus from an adult body cell to an []ty [] [] cell empty unfertilised egg cell.
Adult stem cells are cells that are unspecialised, which can develop into m[], but not [], types of []s many but not all types of cells.
Cells that are unspecialised and can develop into any type of cell are called embryotic stem cells.
Stem cells from embryos and adults offer the potential to treat some illnesses as a result of being unspecialised.
During the early development of multi-cellular organisms: the majority of cells become []d specialised.
During sexual reproduction, []s from both parents come together genes-- and produce []ion in the offspring variation. (The genes detemine the characteristics--variation is difference in a species).
Offspring have some similarities to their parents because of the combination of maternal and paternal []s in the []ed egg alleles--fertilised--. Different offspring from the same parents can different characteristic because they inherit a different []ion of maternal and paternal []s combination--alleles--. This is as the combination is completely random.
To help treat illnesses, stem cells can be grown to []e lost cells replace--. However, to use stem cells and not have them rejected and die because they are treated as foreigners, you need to make sure that receive cells have the same []s as you genes--.
If you were going to recieve medical treatment with cells grown from stem cells, your body's immune system would regard the cells as fo__, and they would be r__ed and d__ foreign--rejected--die--. But this wouldn't happen if the []s were your own. genes
To use stem cells that have the same genes as you, you can []e one of your cells to produce an e[] then take [] []s from this clone-- embryo--stem cells--. This is called []ic []ing therapeutic cloning.
[] stem cells can be specialised into the neccesary adult cell type to produce i[] that could treat people with d[]es Embryonic--insulin--diabetes--.
Ebryonic stem cells can be specialised into the neccesary adult cell type to replace n[]s neurons damaged by s[] c[] injury, A[]'s disease etc spinal cord--Alzheimer--.
Ebryonic stem cells can be specialised into the neccesary adult cell type to replace virtually any t[] or or[] that is injured or diseased tissue--organ--.
recall that instructions to control how an organism develops and functions are found in the [] of its cells nucleus-- and are called genes.
Created by: Toluo
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