Inheritance and Variation

what is a gene

a section of DNA that codes for a particular protein. Genes determine features by instructing cells to produce particular proteins which then lead to the development of the feature. therefore is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

for every feature/character _____

- A 'hertiable unit' (gene) is passed from one generation to the next - The gene can have alternative forms (alleles) - Each individual must have two alternative forms (alleles) per feature - The gametes only have one of the alternative forms (alleles) per feature - One allele can be dominant over the other

Genetic variation due to genetics and environments in humans

- A Child might Inherit the Tendency to be Tall, but a Poor Diet during Childhood will Cause Poor Growth - your language - your religion - flower colour in hydrangeas (these plants produce blue flowers in acidic soil and pink flowers in alkaline soil

Where does mitosis happen more frequently?

-> Skin (we lose cells when we touch something, the layer of cells beneath the surface is constantly dividing to produce replacements) -> Gut (cells are scraped of when food passes the lining of the gut, so constantly dividing to produce replacements ->Spleen (destroy red blood cells. Replaced by cells in the bone marrow dividing by mitosis) -> Cancer (cancer cells divide by mitosis, the mutated gene are divided to exact same copies of the parent cell)

Stages of meiosis:

1) DNA replats to make copies of genetic information cell divides twice forming 4 cells called gametes each with a single set of chromones, half the number of the original cells all genetically different from each other

stages of Mitosis?

1) DNA replicates to form 2 copies of each chromosone 2) cells growth 3) one set of chromosone is pulled to each end of cell 4) nucleus divides to from two nuclei 5) cytoplasm and cell membrane divide 6) 2 genetically identical cells are formed

How are genes determined

1) Each feature is controlled by a gene, which is found on a chromosome 2) There are two copies of each chromosome and each gene in all body cells except the gametes 3) The gametes have only one copy of each chromosomes and each gene (one allele) 4) There are two alleles of each gene 5) One allele is dominant and the other is recessive 6) When two different alleles (dominant and recessive) are in the same cell, only the dominant allele is expressed (shown in the appearance of the organism) 7) An individual can have two dominant alleles, two recessive alleles or a dominant allele and a recessive allele in each cell

what did Darwin observe on his voyage? what does this tell us?

1) Organisms generally produce more offspring the are needed to replace them - a single female salmon can release 5 million eggs per year 2) Despite this over-reproduction, stable, established populations of organisms generally remain the same size 3) Members of the same species are not identical - they show variation He made two important deductions from these observations: - There is a struggle for existence. Many offspring are produced, yet the population stays the same size. There must be competition for resources and many individuals must die - If some offspring survive whilst other die, those organisms best suited for their environment would survive to reproduce. Those less suited will die. Survival of the fittest.

Genetic variation due to genetics and environments in plants

: Pea Plants - can be tall or short - The difference in height is due to the genes they inherit o Not all the tall plants are the same height, same with the short plants - Several environmental factors can influence the height of the plant o Not receive the same amount of light and so some will not photosynthesise as well as others o Not the same amount of water and mineral ions from the soil - effect the range of substances in plant o Not receive the same amounts of carbon dioxide. Some plants some will not photosynthesise as well as others

What is a monohybrid cross?

A cross between two individuals, both heterozygous for one gene - When you bred two organisms together and look at one trait - And what the resulting offspring will have - You can work out the probability of the phenotypes of the offspring

what is a diploid and haploid cell?

A diploid cell is a cell that contains two complete sets of chromosomes. Cells with only half the normal diploid number of chromosomes, and therefore only hald the DNA content of other cells are called haploid cells (eg. gametes)

what is the difference between a gene and an allele?

A gene is a portion of DNA that determines a certain trait. An allele is a specific form of a gene. Function. Genes are responsible for the expression of traits. Alleles are responsible for the variations in which a given trait can be expressed.

example of genetic diagram

These are possible outcomes for the phenotype of the off spring: = 1 x BB, 2 x Bb, 1 x bb = ¼ of blue eye baby (recessive) = ¾ of brown eye baby (dominant)

what is mitosis

two cells are formed. these have the same number of number and type of chromosomes as the original cell. The division of one cell into two genetically identical daughter cells

what is the structure of a chromosome?

two sister chromatids held together by a centromere Each chromosome contains one double-stranded DNA molecule. The DNA is folded and coiled so that it can be packed into a small space. The DNA is coiled around protein called histones.

What is polygenic inheritance?

inheritance pattern of a trait that is controlled by 2 or more genes · As most characteristics in an Organism are controlled by more than one Gene, these Organisms are described as Polygenic · Polygenic characteristics involves Phenotypes that can express a wide range of combinations in features

what is an example of polygenic inheritance

skin colour. Darker skins contain greater amounts of a black pigment called melanin. This is controlled by several genes which act together to determine the amount of melanin in the skin. Each gene has alleles that promote melanin production and alleles that do not. This produces a wide range of phenotypes.

why do cells need to divide?

so organisms can grow and replace damaged/worn out cells. The type of cell should be the same cell as the cells they are replacing. Only in the sex organs cell division is different. Cells divide to produce gametes containing half the original diploid number. So during fertilization -> male and female gametes fuse together (fertilization) resulting in a cell (zygote) which contains a full set of chromosomes, which then can go under mitosis into a new individual.

Sex determination with genetic diagrams:

A genetic diagram shows how alleles may combine in zygotes. The diagram below shows how biological sex is inherited. The two possible combinations are: · an X chromosome from the mother and an X chromosome from the father - producing a girl (female phenotype from the XX genotype) · an X chromosome from the mother and a Y chromosome from the father - producing a boy (male phenotype from the XY phenotype) The ratio of female to male offspring is 1:1 - on average, half of the offspring will be girls and half will be boys. This can also be converted into a probability of 50% (XX) and 50% (XY).

how to use monohybrid cross genetic diagrams?

A male and a female both have 2 alleles each and can pass either one to their offspring. Via sperm or egg (gametes). We can show this using a punnet square: 1) You write down their phenotypes (parents) 2) You write down their genotypes (parents) 3) Then we split them up into gametes (one will go into a sperm, other one in an egg) · Either one of these combinations can be passed on, so we use a punnet square: Upper case letter -> dominant Lower case > recessive

what is the results of the cells after meiosis

All four of these nuclei have variety, due to the crossing over. This variety from the other 3 nucleus and the parent (the parent have 46 chromosomes, these cells have 23. The gametes formed by meiosis don't all have the same combinations of alleles - there is genetic variation in the cells.

what is a genome?

All the DNA in one cell of an organism A genome is the complete set of genetic information in an organism. ... In eukaryotes, each cell's genome is contained within a membrane-bound structure called the nucleus.

How does resistance of antiboitics start?

Antibiotic resistance occurs when bacteria change in response to the use of these medicines. Bacteria, not humans or animals, become antibiotic-resistant. These bacteria may infect humans and animals, and the infections they cause are harder to treat than those caused by non-resistant bacteria. When a ransom mutation gives a bacterium resistance to a particular antibiotic. In a situation where the antibiotic is widely used, the new resistant bacterium has an advantage over non-resistant bacteria of the same type. The resistant strain of bacterium will survive and multiply in greater numbers than the non-resistant type. Bacteria reproduce very quickly. Resistant bacteria will not be killed by the antibiotic, meaning the antibiotic is no longer effective in controlling the disease. This is due to the natural selection and evolution of bacteria.

Codominance Punnet square

Both codominant alleles are shown with upper case letters in genetic diagrams, but the letters used are different For example, feather colour in hens may be white, black or speckled (it has both white feathers and black feathers) The alleles can be shown as W for white and B for black There are three possible genotypes: WW, BB and BW There are also three possible phenotypes: WW = white, BB = black, and BW = speckled

what are homologous pairs?

Chromones with the same genes found at same portions Pairs of matching chromosomes are called homologous pairs. They carry genes for same features, and these genes are arranged at the same positions and sequence along the chromosome. Homologous chromosomes are made up of chromosome pairs of approximately the same length, and shape.

what are chromosomes?

Chromosomes are long, thin strings composed of DNA and proteins -> therefore contains the genes that make up that DNA molecule. Another chromosome will contain a different DNA molecule, and so will contain different

what are these terms? DOMINANT RECESSIVE HOMOZYGOUS HETEROZYGOUS PHENOTYPE GENOTYPE

DOMINANT Characteristic will Show Up in the Offspring Even if Only One of the Alleles is Inherited RECESSIVE Characteristic will Show Up in the Offspring Only if Both Alleles are Inherited HOMOZYGOUS Both Alleles are the Same -> bb HETEROZYGOUS It has Two Different Alleles -> Bb PHENOTYPE Describes the Physical Characteristics of an Organism with Respect to a Particular Pair of Alleles (the Genotype) GENOTYPE Describes the Alleles that a Cell or Organism has for a Particular Feature

What is Darwin's theory of evolution?

Darwin's theory, very simply, is: - Individuals in a species show a range of variation caused by differences in genes - Individuals with characteristics most suited to the environment have a higher chance of survival and more chances to reproduce - Therefore these characteristics are passed to their offspring at a higher rate than those with characteristics less suited to survival - This idea of natural selection became known as 'survival of the fittest'

what is DNA's structure?

Deoxyribonucleic acid ( DNA) is a molecule composed of two chains that coil around each other to form a double helix carrying genetic instructions a molecule of DNA is made from two strands of molecules called nucleotides

why do gametes have haploid cells?

Sex cells only have 23 - half the number of other cells ( they are formed in a process called meiosis). When two games fuse in fertilization, the two nuclei join to form a single diploid cell ( a zygote). The cell has, once again, all its chromosomes in homologous pairs and two copies of every gene. It has the normal DNA content.

what are examples of genes on a person

Genes are sections of DNA that control the production of proteins in a cell. Each protein contributes towards a particular body feature. Sometimes the feature is visible, such as eye colour or skin colour. Sometimes the feature is not visible, such as type of haemoglobin in red blood cells or the type of blood group antigen on the red blood cells. Some genes have more than one form. For example, the genes controlling several facial features have alternative forms, which results in alternative forms of the feature.

Examples of genetics and environment that can change variation

Genetics · Eye Colour · Hair Colour · Blood Type · Inherited Disorders Environment · Lifestyle · Climate · Diet · Culture

how can variation change within a species due genetic, environmental, or a combination of both

Genetics: Variation in a Species can be Caused by Genetics by the Inheritance of Genes and Alleles from Parents Environment: Variation in a Species can be Caused by Environmental Factors, Causing Organisms to Adapt or Change

Explain identical and non identical twins

Identical twins are formed in the same zygote - monozygotic twins. When the zygote divides by mitosis the two genetically identical cells formed do not 'stay together'. Instead they separate and each cell behaves as through it were an individual zygote, dividing and developing into an embryo. Because they have developed from genetically identical cells (and from the same zygote) the embryo and later child will are going to be genetically identical Non identical twins develop from different zygotes and so are not genetically identical

Chromosomes for males and females

Males: XY Females: XX Female gametes (Egg cells) only carry copies of X Chromosomes, Male gametes (Sperm Cell) determines the sex of the offspring as they can carry either an X or Y Chromosome, therefore capable of producing a Male or a Female

How does natural selection work?

Many gene mustations are harmful, and cells that carry them will not usually survive. Some mutations are 'neutral' and if they arise in the gametes, may be passed on without affecting the survival of the offspring. However, a few mutations can work beneficially to an organism. Beneficial mutations are the 'raw material' that are ultimately the source of new inherited variation.

What is meiosis

Meiosis forms gametes. This takes place in two stages meiosis I and meiosis II, resulting in 4 haploid cells. Each daughter cell is genetically DIFFERENT from the other three and from the parent cell.

Can we obverse natural selection in action?

Most animals and plants reproduce slowly, so it takes a long time for natural selection to have an observable effect.t to obverse natural selection happening we can study an organism that reproduce quickly, being bacteria or insects.

What are mutations?

Mutations are rare and random changes to the genetic code of a person. It can be inherited.This is done by changing the sequences of the DNA bases, which could stop the production of a specific protein/produce a different kind of protein, leading to new characteristics.

what are natural antibiotics

Natural antibiotics are produced by bacteria or fungi. They give a microorganism an advantage over other microorganisms when competing for nutrients and other resources, since the antibiotic kills the competing organisms

how many chromosomes in the human body

Nearly all human cells contain 46 chromosomes. Human body cells each contain 23 pairs of chromosomes, half of which are from each parent. there are 44 non-sex chromosomes and 2 sex chromosomes. Not all human cells have 46 chromosomes. Red blood cells have no nucleus and so have none. This shows a man's chromosomes. One of each of the 22 homologous pairs, along with the X and Y sex chromosomes.

how does random fertilisation produces genetic variation of offspring

Sexual reproduction in many multicellular organisms involves the fusion of two gametes to form a zygote. The offspring from sexual reproduction vary genetically for a number of reasons: 1) The huge variation of gametes 2) Random way in which fertilization takes place -> billions of sperm fertilise one of the thousands of ova This variation happens in female and male gametes. When fertilization takes place any sperm could fertilize with any ovum. The number of possible combinations of chromosomes (and genes) in the zygote is A LOT! This means the individual is going to be genetically unique - except identical twins. same with plants: different pollen grains fertilizing different egg cells and so contain different combinations of genes.

What is Codominance?

Some genes have alleles that are equally dominant and so are both expressed equally in the phenotype This is known as codominance

what is DNA and what is the importance of it

The chemical that is the basis of inheritance in nearly all organisms is DNA. store genetic information

example of gene and allele

The gene for earlobe attachment has the forms 'attached earlobe' and 'free earlobe'. These different forms of gene are called alleles. Homologous chromosomes carry genes for the same features in the same sequence, but the alleles of the genes may not be the same. The DNA in the two chromosomes might not be identical A and a, B and b and C and c are different alleles of the same gene. They control the same feature but code for different expressions of that feature.

what is evolution and how is it connected to natural selection

The meaning of 'evolution' is that a species of animals and plants are not fixed in their form, but change over time. What was missing is the mechanism by which evolution could have occurred. This 'mechanism' is natural selection

What are family pedigrees

To show family history of genetic condition requires more than just a genetic diagram. We can use a diagram called a pedigree

Example of natural selection, The Hoverfly:

Wasps can defend themselves against predators using a sting. They also have a body with black and yellow stripes. This is called a 'warning colouration'. Predators such as birds soon learn that these colours mean that wasps have the sting, and they avoid attacking them. Hoverflies do not have a sting, but they have an appearance that mimics a wasp. Predators treat hoverflies as if they do have a sting. Mimicking the wasp is a advantage to the hoverfly. But how did this happen? - The selection pressure was prediction by birds and other animals. Among the ansestors they would have been variations of colours - As a result of mutations some hoverflies gained genes that produced stripes on their bodies. - These were less likely to be eaten by predators compared to the ones without the stripes. They had a selective advantage - Since the hoverflies with stripes were more likely to survive, they were more likey to reproduce and so pass on the genes for stripes onto their offspring - This process continued over many generations. Gradually more mutations and selection for 'better' stripes took place.

What are antibiotics? exmaple?

chemicals that kill or reproduce the growth of microorganisms. They are used in medicine mainly to treat bacterial infections, although a few antibiotics are effective against fungal pathogens. Antibiotics do not work on viruses so they are no use in treating any disease caused by a virus. What is an example of antibiotic? -> Penicillin - kills bacteria

Where is DNA found?

found in the nucleus of a cell, in the chromosomes

Example of pedigree

we can extract a lot of information from a pedigree. In this case: - There are four lines of generations - Individuals 4,5 and 6 are children of individuals 1 and 2 ( a family line connects them) - Individual 4 is the first born child of 1 and 2 (the first born is shown to the left, then the second to the right of this etc) - Individuals 3 and 7 are not children of 1 and 2, no family line - Individuals 3 and 4 are father and mother of the same children - as are 1 and 2, 6 and 7, 8 and 9, 12 and 13, 14 and 15 ( a horizontal line connects them) we can see, interpret and fill in They could be homozygous or heterozygous. For example individuals 1 and 2 are both heterozygous. you can use a punnet square to see the possible outcomes. Individual 5 could be anu of the outcomes indicated by the shading. It is impossible to distinguish between DD and Dd

what is the problem with antiboitics?

· With the increase in population of antibiotic-resistant Bacteria, there is difficulty curing and controlling bacterial infections and diseases While research for new antibiotics are ongoing, Superbugs - a type of Bacteria that is resistant to all known antibiotics, raises concerns about the effectiveness of antibiotics in the future