Inheritance and Variation Flashcards

Question

Recessive trait

Answer 1

An inherited trait that results from the presence of two identical recessive alleles. It is only seen in an individual with with no dominat allele

Answer 2

In the IMPATIENS plant allele R stimulates red flowers allele W stimulates white flowers. When an impatien plant with red flowers allele RR is crossed with a plant wit white flowers WW, neither allele is dominat over other and a pink flower is produced, RW is genotype

Answer 3

Normal haemoglobin A Abnormal allele stimulates the production of abnormal haemoglobin. These alleles show co dominance Hb^A Hb^S 55-65% normal haemoglobin A 35-45%- abnormal haemoglobin S Sickle cell anameia may develop in low oxygen conditions high altitude strenuous physical exercise

Answer 4

Controlled by three alleles I^A I^B I^O A and B are both dominant to O A and B are co-dominant Only two alleles are present in any cell E.g. I^B I^O blood group is B

Answer 5

Used by genetic counsellors to identify potential risks for offspring developing a genetic disorder - dominant (BOLDED and Capital letter) - recessive (NOT BOLDED AND COMMON LETTER) -female is a circle male is square -horizontal line for marriage and sex -vertical downwards for children/offspring -if the PARENTS produce a child with that's recessive AT LEAST ONE OF THEM MUST BE A CARRIER (Aa heterozygous) -if it is unbolded recessive and therefore no dominant allele aa tt -if they produce at least one offspring that's a carrier or recessive they both have a recessive allele or heterozygous - only people people borne of people with the dominat trait and are dominant themselves are homozygous AND heterozygous

Answer 6

Characteristics determined by genes found on sex chromosomes only that have nothing to do with determining gender EXAMPLE X^R

Answer 7

One pair is sex chromosomes. XX genotype is women XY is male. Since the male is the only parent that can carry on the Y chromosome, males determine the sex of the offspring

Answer 8

Sex linked condition in which blood fails to clot a cut. In haemophilia and colour blindness only the x chromosomes carry the alleles. As a result males are more likely to have the condition as they only hv one X chromosome and if that one has a recessive trait they have the condition however since females have two X chromosomes BOTH MUST CARRY YHE RECESIVE ALLELE IN ORDER TO HAVE THE CONDITION

Answer 9

Continous AND Discontinous NO two organisms are completely identical. PHENOTYPES all living organisms have thus EXPLAIN WHAT IT IS

Answer 10

Heterozygous Aa

Answer 11

**Meiosis** Every gamete produced by meiosis has a different combination of genes as result of: - chromatids of homologous chromosomes crossing over and exchanging genes -chromosomes arranging themselves around the equators of the spindles in totally random ways **Sexual Reproduction** **Mutations

Answer 12

During fertilization , male and female gametes fuse in completely random ways to create different combinations of genes in each zygote.

Answer 13

A mutation is a sudden change in a single gene or in part of a chromosome containing several genes. Mutations cause new characteristics to suddenly develop in organisms. Mutations occurring in body cells cannot be inherited whereas mutations occurring in a gamete or zygote can be inherited. Most mutations are harmful; however, a few produce beneficial characteristics which provide the organism with a selective advantage in the struggle for survival, e.g . the peppered moth (see page 159).

Answer 14

Living organisms are constantly affected by the different factors in their environment. Food, drugs, physical forces, temperature and light can affect animals, Temperature, light intensity, availability of mineral salts and water all affect plants. This variation is not caused by genes and cannot be passed on to offspring

Answer 15

- It enables species to adapt to changing environmental conditions, improving their chances of survival. - It provides the raw material on which natural selection can work, and is therefore essential for species to remain well adapted to their-environment or GRADYALLY CHANGE AND GET BETTER. -It makes it less likely that any adverse changes in environmental conditions will wipe out an entire species since some organisms may be able to adapt to the new conditions

Answer 16

Continuous variation is where characteristics show a continuous gradation from one extreme to the other without a break. Most organisms fall in the middle of the range with fewer at the two extremes,.i.e. the characteristics show a normal distribution. Examples include height, weight, foot size, hair colour, and leaf size in plants. Characteristics showing continuous variation are usually controlled by many genes and can be affected by environmental factors.

Answer 17

Discontinuous variation is where characteristics show clear cut differences with no intermediates. Individuals can be divided into distinct categories, e.g. ABO blood groups, tongue rolling, and the presence or absence_of horns in cattle. Characteristics showing discontinuous variation are usually controlled by a single gene and environmental factors have little, if any, influence on them.

Answer 18

The formation of new species. As long as organisms from different groups within a species can interbreed and genes can flow between them, the groups remain members of the same species. If groups become separated or isolated, the flow of genes between them stops. Genetic differences gradually develop and a point is reached where members of the groups can no longer successfully interbreed. They become separate species, each with its own pool of genes

Answer 19

This occurs when a physical barrier-prevents two groups of organisms of the same species from meeting and interbreeding. Such barriers include mountain ranges, deserts, oceans, rivers or even streamS.

Answer 20

Speciation can occur when two groups of organisms of the same species inhabit the same region but they become adapted to different habitats in that region, which reduces-gene flow. Behavioral Speciation can also occur when animals exhibit elaborate courtship behaviours before mating, which may be stimulated by the colour, markings, calls or actions of the opposite sex. If small differences occur in any of these stimuli it can prevent mating, which prevents gene flow.

Answer 21

Over time species can also become extinct, i.e. they no longer exist. Habitat loss, disease, predation by introduced species, competition with introduced species or overexploitation by humans, e.g. overfishing or overhunting, can all lead to extinction of species. For example, the Caribbean monk seal has become extinct due to it being overhunted for its fur, meat and oil.

Answer 22

Natural selection is the process by which populations change over time or evolve, so that they remain well adapted to their environment.

Answer 23

* Most organisms produce more offspring than are needed to replacethem, yet the numbers ofindividuals in populations remain relatively constant. In nature there must, therefore, be a constantstruggle for survival. *All organisms show variation and much of this can be inherited. Those organisms possessingvariations that make themwell adapted to their environment are most likely to survive in thestruggle, i.e. there is survival of the fittest. * Since the well adapted organisms are the most likely to survive, theyare the ones most likelyto reproduce, thereby passing on their advantageous characteristics to their offspring. Species,therefore, remain well adapted to their environment or they gradually change andimprovebybecoming even better adapted. Natural selection preserves useful adaptations

Answer 24

The peppered moth lives in Britain and is eaten by birds. Before the Industrial Revolution, the moths were black andwhite speckled and were well camouflaged against the pale lichen-covered tree trunks on which they rested. During the Industrial Revolution, a melanic (all black) variety appeared in the industrial area around Manchester. Thismelanic variety arose as a result of a dominant mutation and was well camouflaged against the tree trunks which were blackened with soot. This gave the melanic variety a selectiveadvantage in industrial areas and, over time, it became far more numerous in these areas than the speckled variety.

Answer 25

In natural populations of bacteria and various pests, e.g. insects, fungi and weeds, a few individualsmay carry genes that make themresistant to antibioticsor various pesticides, e.g. insecticides, fungicides and herbicides. These genes arise from mutations. When exposed to antibiotics orpesticides, these resistant organisms have a selective advantage; they are more likely to survive and reproduce than non-resistant organisms, passing on their resistance to their offspring. Thisis causing increasing numbers of resistant organisms to appear within populations.

Answer 26

Anole lizards are thought to have colonised theislands of the Caribbean from Central and SouthAmerica. Through natural selection, lizards strandedon the four larger islands of Cuba, Hispaniola, Jamaica and Puerto Rico independently evolvedinto different species with similar characteristics that enabled them to fit similar ecological niches on each island, e.g. twig anoles developed long, slender bodies and tails and short legs; trunk ground anoles developed long, muscular legs, andcanopy anoles developed large toe pads. Today, the different species have equivalent species with similar body types on each island.

Answer 27

Artificial selection involves humans selectingandbreedingorganismsshowingdesirablecharacteristics. As a result, newbreeds, strains or varieties of plants and animals are produced with characteristics to suit human needs.

Answer 28

It has the disadvantage that it reduces variation in populations making them more vulnerable if environmental conditions change.

Answer 29

Inbreeding involves breeding closely related individuals showing desirable characteristics. It is usually used to improve one particular trait. Continued inbreeding reduces the gene pool whichincreases the frequency of undesirable genes and reduces the overall fitness of the organisms. After several generations of inbreeding, outbreeding must take place to introduce new genes into a population

Answer 30

Outbreeding involves breeding individuals from genetically distinct populations showing desirable characteristics. Offspring produced are called hybrids and usually show characteristics that are superior to both parents. This is known as hybrid vigour.

Answer 31

* Increased yields, e.g. cattle that produce more milk or meat, chickens that lay more or larger eggs, sugar cane that produces more sucrose and cereal crops that produce more grain. * Increased quality of product, e.g. meat with less fat, andcereals and ground provisions with a higher protein content. * Faster growth rates. * Increased number of offspring. * Shorter time to reach maturity so that more generations are produced per year. * Increased resistance to pests and disease. This reduces product loss and the need for pesticides. * Increased suitability to the environment.

Answer 32

* Jamaica Hope, a breed of dairy cattle,the breed is heat tolerant, has a high resistance to ticks and tick borne diseases, and produces a high yield of milk, even when grazing on the poor pasturelands of the Caribbean. * Sugar cane has been bred to produce varieties with a high sucrose content, increased resistance to disease and insect pests, greater suitability to its environment and improved ratooning ability.

Answer 33

Genetic engineering involves changing the traits of one organism by inserting genetic material from a different organism into its DNA. The organism receiving the genetic material is called atransgenicorganism or genetically modified organism (GMO).

Answer 34

* Protect agricultural crops against environmental threats, e.g. pathogens, pests, herbicides and low temperatures. * Modify the quality of a product, e.g. increasing nutritional value. * Make organisms produce materials that they do not usually produce, e.g. vaccines and drugs. * Improve yields, e.g. increasing size or growth rate, or making organisms more hardy.

Answer 35

By inserting two genes into rice plants, one from maize and one from a soil bacterium, theendosperm of the rice grains is stimulated toproduce beta-carotene which the body converts to vitamin A. Golden rice should help fight vitamin A deficiency which is a leading cause of blindness, and often death, of children in many underdeveloped countries.

Answer 36

By inserting a gene from a soil bacterium into certain crop plants, e.g. soya bean, corn and canola, the plants become resistant to theherbicide called ‘Roundup’. The herbicide can be sprayed on the crops to destroy weeds, but not harm the crops.

Answer 37

By inserting a gene from a soil bacterium into corn plants, the plants are stimulated to producea chemical that is toxic to corn-boring caterpillars. This makes the corn plantsresistant tothe caterpillars.

Answer 38

* Insulin By transferring the gene that controls insulin production in humans into bacteria, the bacteria produce insulin which is used to treat diabetes. * Human growth hormone (HGH) By transferring the gene controlling the production of HGH into bacteria, the bacteria produce the hormone which is used to treat growth disorders in children. * Hepatitis B vaccine By transferring the gene controlling the production of hepatitis B antigens in the hepatitis B virusinto yeast, the yeast produces the antigens whichare used as a vaccine. Other drugs produced by genetic engineering include: * Blood clotting drugs for people with haemophilia. * Follicle stimulating hormone (FSH) used to stimulate the ovaries to produce mature ova in women that are infertile

Answer 39

Some benefits of genetic engineering in agriculture are increased crop yields, reduced costs for food or drug production, reduced need for pesticides, enhanced nutrient composition and food quality, resistance to pests and disease, greater food security, and medical benefits to the world's growing population.

Answer 40

1. Once a genetically modified organism is released into the environment, it cannot becontained orrecalled. Any negative effects are irreversible. 2. * The number of allergens in foods could be increased by transferring genes causing allergic reactions between species. 3. * unknown health risks may occur as a result of eating genetically modified plants andanimals. 5. * Large companies with funds and technology to develop genetically modified organisms could make large profits at the expense of smaller companies and poorer nations. 7. *Difficult moral and ethical issues' 8. Increased Weediness.

Answer 41

DNA testing or DNA fingerprinting DNA testing involves analysing specific regions of DNA taken from cells of individuals

Answer 42

Gene therapy Gene therapy is an experimental technique that involves altering genes inside body cells to cure a disease or help the body fight a disease. 1. By inserting a functional gene into cells to replace a defective gene that causes a disease. 2. By inactivating or ‘turning off’ a defective gene that causes a disease. 3. By introducing a gene into cells to help the body’s immune system tofight a disease.