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OCR 21st Cen Sci. B1
B1
| Question | Answer | |
|---|---|---|
| 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. |
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Toluo
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