🧬variation & inheritance🧬

where is the genetic information carried?

in the nucleus cells and is passed from generation to generation during reproduction

chromosomes

made up a large molecules of a special chemicals called DNA (deoxyribonucleic acid)

DNA

long molecule made up of two strands that are twisted together to make a spiral

units of inheritance

each of your chromosomes contains thousands of genes joined together

what are the properties of genes?

controls what an orgnaism is like and determines the size,shape, colour

inherited traits

physical or behavioral features that are passed from parents of offspring through genes

• examples: eye colour, hair texture, etc…

acquired traits

characteristic or attitude that organsims develop during their lifetime due to experiences and environmental influence

• examples: reading skills, playing a musical instrument, etc…

why do chromosomes in pairs?

because we inherit one set from each parent, which allows for genetic diversity, ensures traits are passes down, and provides a backup if one chromosome has a problem. Humans have 23 pairs, including one pair of sex chromosomes

why do genes come in pairs?

because chromosomes that carry genes come in pairs. We inherit one copy of each gene from our mother and one from our father. This pairing allows for genetic diversity and ensures there’s a backup copy of each gene, which one help if one copy is faulty

what are the two types of reproduction?

sexual and asexual

what’s another name for sex cells?

gametes

how many chromosomes do egg and sperm have?

23

allele

alternative of a gene

what are the properties of asexual reproduction?

• only involves one parent

• gives rise to genetically identical offspring known as clones

• the cells in your body divide into two identical cells for growth and to replace worn-out tissues

what are the advantages of asexual reproduction?

• many identical offspring can be produced when conditions are favourable which is faster

• more efficient because only one parent is involved in the process of reproduction

what are the disadvantages of asexual reproduction?

• no genetic variation - new diseases to a single organism may destroy the whole

• cannot adopt to environment

what are the properties of sexual reproduction?

• involves a male sex cell and a female sex cell from two parents

• these two special sex cells (gametes) join together to form a zygote which goes on to develop into a new individual

what are the gametes in plants?

ovales and pollen

what are the gametes in animals?

ova (eggs) and sperm

why is sexual reproduction so important?

The variation it produces is a great advantage in making sure that a species survives. Variation makes it more likely that at least a few of the offspring will have the ability to survive difficult conditions

gamete

a reproduction cell (sperm or cell) that contains half the genetic information of the parent

variation

differences in characteristics among individuals of the same species, caused by genetic or environmental factor

what is the new plant produced by?

asexual reproduction

in asexual reproduction, how do body cells divide?

mitosis

haploid cells

contains just half of the number of chromosomes and gametes

diploid cells

almost all other cells, complete number of chromosomes

meiosis

a form of cell division which produces four non-identical, haploid sex cells or gametes

what happens when a meiosis cell divide to form gametes?

• copies of the genetic information are made

• the cell divides twice to form four gametes, each with a single set of chromosomes

• gametes are haploid

• all gametes are genetically different from each other

what are the causes of variation?

• some differences between the organisms of a species are entirely due to the environment they live in

• genetically identical plants can be grown under different conditions of light, carbon dioxide, or nutrients or don’t make as much food as plants with plenty of everything

  • will be smaller and weaker

  • haven’t been able to fulfill their genetic potential

what’s the same ONLY genetically identical humans?

identical twins who came from the same fertilised egg

continuous variation

gradual transition between two extremes

• features are determined by a number of different genes are affected by the environment

discontinuous variation

little or no environment impact on the features

• features are determined by a single gene (or chromosome)

• genes control the development of characteristics

  • may be changed by the environment

how many pairs of chromosomes do humans have?

23 pairs of chromosomes

• each chromosome in the pair is a similar shape

sex chromosome

one pair of is different

• two X chromosomes: female

• one X chromosomes + a smaller one, Y chromosomes: male

Parents: Genetype = XX x YY

Phenotype = female x male

genotype

genetic make-up of an individual regarding a particular characteristic

phenotype

the physical appearance of an individual regarding a particular characteristic

dominant allele

alleles that control the development of a characteristic even when they are only present on both chromosomes

recessive alleles

alleles that only present on both chromosomes

homozygous

an individual with two identical alleles for a characteristic

heterozygous

an individual with different alleles for a characteristic

monohybrid crosses

genetic cross involving the inheritance of a single gene

what does a punnett square show us?

• the alleles for a characteristic carried by the parents (the genotype of the parents)

• the possible gametes which can be formed from these

• how these combine to form the characteristic in their offspring

what are the family tree annotations for mother and father genotype?

• mother genotype = ee

• father genotype = EE

a family tree diagram

a model of inheritance showing characteristic was passed from parents to offspring

what is the property of a carrier of a recessive genetic disoder?

• a carrier of a recessive genetic disorder does not express the disorder in their phenotype but one recessive allele in their genotype that can be passed to offspring

inheritance

the passing of genetic information from parents to offspring by reproduction

diagram of a family pedigree

nucleotides

the building blocks of DNA

• four different types

• linked together to form strands

base

part of nucleotide that can make it different from others

double helix

two strands of nucleotides twisted around each other to form a shape

what holds a double helix’s two strands together?

by weak bonds between pairs of bases

what determines the sequence of bases in a DNA molecule?

can determine the order of animo acids in a protein molecule

what’s the 2 different location where the instructions for making proteins and the structures where protein are made?

• DNA is stored in the nucleus

• ribosomes

ribosomes

proteins are assembled from free amino acids in the cytoplasm in structures

how is the chemical messenger RNA (MRNA) mode?

made in the nucleus and carries a copy of the DNA base sequence of a specific gene to the cytoplasm

polydactyly

a dominant condition where a body is born with extra finger or toes

• it can be inherited from one parent who has the condition

what are the properties of polydactyly’s?

• if one your parents has polydactyl and is heterozygous, you have a 50% (one in two) chances of inherit the disorder

  • because half of their gametes will contain a faulty a dominant allele

meiosis

results in the formation of four genetically non-identical daughter cells

• used in sexual reproduction

what are the 4 features of asexual reproduction ?

• no gamete fusion

• offspring are clones

• cells divide by mitosis

  • two sets of chromosomes are pulled to opposite ends of the cell, then the nucleus divides into two

• only one parent

what happens to cell in the reproductive organs?

divide by meiosis to create gametes (contain half of the number of chromosomes which contains DNA found in all body cells

how are gametes formed, and what happens during meiosis?

gametes are formed through meiosis, where a diploid cell replicates its chromosomes, splits into two, and divides again to create 4 genetically different haploid cells

what happens after fertilisation?

the make and female gametes fuse to form a zygote with 46 chromosomes. The zygote with 46 chromosomes. The zygote then divides by mitosis, and as it grows into an embryo, its cells differentiate to perform specific functions

what are the advantages of sexual reproduction?

• variation in offspring: increases the chances of the population being able to survive environmental change by natural selection

• artificial selection: humans can speed up artificial selection breeding of plants & animals

  • depends on genetic variation

what are the advantages of asexual reproduction?

• no mate

• faster

• lots of identical offspring

what are the levels of organisation?

• DNA: double helix polymer

  • means it’s a polymer (a large molecule made up of many subunits) made up of two strands forming a twisted shape

• genes: a small section of DNA

• chromosomes: long strands of DNA are coiled up to form chromosomes

  • humans body cells contain 23 pairs of chromosomes, one of each pair coming from each parent

domaint allele

always expressed

• only needs one copy present to be expressed (BB or Bb)

recessive allele

only expresses if the other allele is also recessive

• needs two copies to be present to be expressed (bb)

genetype

combination of alleles an organism has

• if the two alleles are different, we say that the person is heterozygous (Bb)

• if the two alleles are the same, we say that the person is homozygous (BB or Bb)

phenotype

alleles present will determine a characteristic, unless the environment interferes

what is the name of the diagram that can used to visualise the outcome of monohybrid cross?

punnet square

how can punnet squares be used to visualise the outcome of a monohybrid cross?

1) the alleles of the parents are drawn along the top and side of a grid

2) in the punnet square diagrams, a capital letter shows a dominant allele

3) the pairs of alleles that the offspring could have are then filled into the grid in the four middle squares

what are family rees can be used to visualise?

the transmission of inherited disorders from one generation to the next

what form of genome screening can be used to prevent a baby growing up suffering with a genetic disorder?

embryonic screening

what are the disadvantages of embryonic screening?

• since the embryo that aren’t are destroyed, this can be unethical

• expensive

• discrimination

• parents become selective

what are the two types of chromosomes?

• males: XY; so a sperm contains either one X or Y one chromosome

• females: XX; so an egg contains one X chromosome

what are the differences in variation?

• genetics (inherited genes)

• genetics and environment

• the environment

what does speciation happen?

happens when the average phenotypes (observed characteristics) of two populations have diverged (changed) so much that the populations can longer breed to produce fertile offspring (offspring can reproduce)

what are the properties of natural selection?

• the characteristics that maximise survival chances are passed on

• individuals display genetic variation

• those with the best characteristics are more likely to breed

what does selective breeding happens?

happens when humans chose animals and crops to breed, based on their genetic characteristics

after breeding parents with the desired characteristic, what is the next step in the selective breeding process?

from the resultant offspring, chose the ones who most strongly display the desired characteristics and breed them

what are the 2 most common reasons for a characteristic being considered desirable?

usefulness and appearance

what are the problems of selective breeding?

• Inbreeding: some breeds become particularly susceptible to disease or inherited defects

• Reduced variation: makes it harder for a species to adapt to environmental change

what are the properties of genetic engineering?

• modifying an organism’s genome

• introducing a gene from another organism

what type of crops are through by some people to negatively impact wild flower and insect populations, and reduce biodiversity?

GM crop

what are the ways plants can be cloned?

• tissue cultures

• cuttings