Biology Topic 3

Autosomal disease in humans

*not on sex chromosomes Most genetic diseases are caused by autosomal recessive alleles. This means that to get the disease, you have to have two bad alleles for the disease. This also means that people who are heterozygous have one bad allele but don't get sick, they are carriers. Two healthy carriers can have a sick child.

Method of cloning Dolly the sheep

1) From the original donor sheep to be cloned, a somatic cell from the udder was collected and cultured and the nucleus was removed. 2) An unfertilized egg was collected from another sheep and its nucleus was removed. 3) Using an electrical current, the egg cell and the nucleus were fused together. 4) The new cell developed in vitro, and started to form an embryo. 5) The embryo was placed in the womb of a surrogate sheep. 6) The embryo developed normally. 7) Dolly was born

Steps for making a karyogram

1) cells are stained and put put on a slide to look at under a microscope 2) a picture is taken of a cell in metaphase 3) chromosomes are cut/pasted into order by size, largest to smallest, and position of the centromere 4) sex chromosomes are last

How many different gametes could a human produce?

2²³, or 8,388,608. That doesn't include crossing over.

How many chromosomes do humans have?

46, 2 sets of 23

Peculiarity with blood types

A and B are both dominant while O is recessive. Only one way to be Type O - ii. Only one way to be Type AB - I^A I^B. Two ways to be Type A or Type B.

achromatopsia

A condition where you cannot see color, caused by a single base change concerning the production of transducin on chromosome 1

How can parents find out if their child has down syndrome?

A karyotype will show whether a child has a chromosomal abnormality or not.

Gene splicing

A plasmid is removed from the host cell and cut open using a restriction endonuclease. The gene to be copied is placed inside the open plasmid, which will then copy the DNA.

Pedigree

A record of an organism's ancestry. Can be made to show biological relationships. They can show how a trait is passed from generation to generation. Symbols used to represent people: ◯ Female, ⬜ Male. If filled in, represents the trait being studied. Horizontal line between shows mating. Vertical line shows offspring.

Common autosomal dieases

Albinism, Cystic Fibrosis, Phenylketonuria (PKU), Sickle cell disease and trait, Tay Sachs, Thalassemia

Methods for obtaining cells for karyotyping unborn

Amniocentesis and Chorionic Villus Sampling

Methods of obtaining cells for karyotyping

Amniocentisis - taking amniotic fluid, or Chorionic Villus Sampling - taking a piece of tissue from the placenta. CVS is faster, but it more dangerous

Hydra vulgaris

An invertebrate that can asexually reproduce by budding

Gregor Mendel

Austrian monk who discovered the principals of inheritance by experimenting with pea plants. Didn't know about genes of DNA. Studied to find out what had to happen to get the desired result in the plants.

Division II of meiosis

Basically is mitosis

Why is DNA attracted to the histones?

Because the DNA has a negative charge and the histones have a positive charge

The human genome project now

Before the project, they knew where fewer than 100 genes were that caused disease, they now know 1400. They are now working on what each gene does. As this happens, scientists know where the locus of individual genes and what they do.

Human genome project

Began trying to sequence the human genome in 1990. In 2003, they announced they had sequenced the entire human genome.

Example of multiple alleles

Blood type - alleles are A, B, and O so there are 6 possible genotypes, AA, Ao, BB, BO, AB, and OO.

Punnett square

Can be used to show the possible gametes of parents to predict the possible outcomes of a cross. If for one trait, called a monohybrid cross.

Huntington's disease

Caused by a dominant allele - H. So, everyone who has it has a parent who has it.

sickle cell anemia

Caused by a single base substitution mutation in the gene that is responsible for producing hemoglobin. The mutation causes hemoglobin to have a sickle shape which prevents it from carrying oxygen efficiently and causes clots because valine is added to the change instead of glutamic acid.

Anaphase II

Centromeres split and sister chromatids move toward the poles. In animals, cell membranes begin to pinch in. In plants, cell plates begin to form.

Phenotype

Characteristic or trait of an organism ex) blue eyes, type A blood

Prophase I

Chromosomes coil and become visible. Nuclear membrane begins to break down. Spindle fibers form, nucleolus disappears. Homologous chromosomes are attracted to each other. Crossing over occurs.

Telophase II

Chromosomes unwind, nuclear membranes form. Cytokenisis occurs to form 4 haploid gametes.

Examples of sex linked traits

Color blindness, Hemophilia, Duchene muscular dystrophy, white eye color in fruit flies, calico-tortoiseshell fur in cats

How DNA profiles are analysed

Comparing the banding patterns of the images of DNA obtained through gel electrophoresis

How do cells create variation?

Crossing over during Prophase I and random orientation during Metaphase I. Sexual reproduction also creates variation because of which of the different sperm cells fertilizes the egg cell.

What are chromosomes made of?

DNA - The DNA is wrapped twice around 8 histone proteins forming an area called a nucleosome (sometimes a ninth histone)

Prophase II

DNA condenses into visible chromosomes. spindle fibers are produced, nucleolus disappears.

How do the chromosomes prepare for meiosis?

DNA is replicated prior to meiosis, so each of the 46 chromosomes look like an x, two sister chromatids connected by the centromeres.

Carl Woese

Discover Archaea while studying mutations in genes

Random orientation

During metaaphase of the first division, the homologous chromosomes are going to line up side by side in the middle of the cell. How they line up is random. This also increases variation within the gametes.

Crossing over

During the first division of meiosis, the homologous chromosomes pair up side by side. DNA is exchanged between the chromosomes, which allows the mother's DNA to mix with the father's DNA to increase variation within the gametes. The new chromoatids are called recombinant chromatids.

Uses of gene splicing/DNA cloning

E. coli has successfully made human insulin. The older technique for obtaining insulin involves extracting it from cow and pig carcasses from the meat industry, but this has caused allergy problems.

Cutting and pasting DNA

Endonucleases (restriction enzymes) 'cut' the DNA so it can be released and removed. Then ligase attaches the base sequences to the DNA.

Sickle cell disease and malaria

Having one or two sickle cell alleles prevents malaria

Metaphase I

Homologous chromosomes line up along the equator by random orientation. Nuclear membrane is gone. Spindle fibers grow toward the chromosomes.

Co-dominance in a flower

In some flowers, a red allele and a white allele will give you a pink flower. We will call the gene C for color. C^R is red. C^W is white. C^R C^R = red C^W C^W = white C^R C^W = pink

The value of the human genome project

Information learned from the human genome project can help scientists study evolutionary pattern and how we migrated over the past. If we the genes are for making a certain protein, we can then use that gene in the lab to make molecules for people who can't make them due to genetic abnormalities.

Ethical issues surrounding therapeutic cloning

Is it ethically acceptable to generate a new human embryo for the sole purpose of medical research? In nature, embryos are created only for reproduction, and many people believe that using them for experiments is unnatural and wrong.

How is down syndrome caused by non-disjunction?

It causes some eggs to have 2 chromosome 21s and others to not have any.

Therapeutic cloning

Its aim is to develop cells that have not yet gone through the process of differentiation. As the first technique in this area involved using embryos, the cells are referred to as embryonic stem cells

Punnett square example (albinism)

Lets call the allele for pigment A and the allele for no pigment a. Both parents in this example are heterozygous.

Difference between mitosis and meiosis.

Mitosis is a 2n nucleus creating two 2n nuclei. Meiosis is a 2n nucleus creating four n daughter cells.

Causes of mutations

Mutations can result in genetic diseases and cancer: radiation (Marie Curie with radium, died of leukemia, Hiroshima), power plants, X-rays, UV, carcinogens (cancer-causing chemicals)

Can you patent a gene?

No

Do different alleles have different loci?

No

Do all people have 46 chromosomes?

No, sometimes organisms end up with less or more chromosomes than normal due to non-disjunction, which usually occurs during Anaphase I.

Metaphase II

Nuclear membrane gone. Individual chromosomes line up randomly on the equator. Spindle fibers attach to the centromeres.

Chorionic Villus Sampling

Obtains cells from the placenta's finger-like projections called villi.

Cystic Fibrosis

On chromosome 7. The good allele is called F and the bad one is f. FF homozygous dominant - okay. Ff heterozygous (carrier) - okay. ff homozygous recessive - have the disease.

Value of PCR

PCR is used to solve the problem of how to get enough DNA to be able to analyse it. By using PCR, forensics experts or research technicians can obtain millions of copies of the DNA in just a few hours.

Application of DNA profiling

Paternity suits, studying ecosystems/evolution, crime investigation - many innocent men and women have been liberated after being sent to jail for a crime they did not commit

Transgenic plants

Plants, mostly food, which have had an undesirable gene taken out, or have had a desirable gene put in.

Traits of homologous chromosomes

Same genes in the same locus, but not necessarily the same alleles.

How do geneticists figure out a genome?

Sanger technique - DNA samples are chopped into pieces, and copies are made (PCR). 1) Primer added to start replication. 2) Each piece is put into DNA polymerase and the 4 nucleotides so that replication can occur. 3) Each time, a special tagged base is tested which, if added to the chain, will stop replication. 4) The pieces will all end with the tagged nucleotide and all the pieces are run through gel electrophoresis.

Dolly the sheep

She was the first clone whose genetic material did not originate from an egg cell.

Example of transgenic animals

Sheep being used to produce large amount of factor IX for people with hemophilia

Anaphase I

Spindle fibers attach to centromeres of chromosomes and pull the toward the poles.

Telophase I

Spindle fibers disintegrate. Chromosomes uncoil, nuclear membranes form. Many plants don't have Telophase I. Cytokinesis occurs and creates 2 haploid cells.

Natural methods of cloning

Strawberries can send out horizontal structures to allow a new strawberry plant to grow, if you plant a potato it will grow into a new plant

Correlation between mother's age and trisomy 21.

Studies of families with children who have Down Syndrome show that the age of the mother shows the highest correlation. The older the mother is, especially after 30, the greater the odds.

Test cross

Testing an organism that shows the dominant trait to find out if it's homozygous or heterozygous by crossing it with a known recessive. ex) Is it AA or Aa? Cross with aa to find out

Sex-linked alleles

The allele of concern is located (locus) on a sex chromosome, usually the X because it is so much larger. Usually affects one sex more than the other.

Gene transfer

The genetic engineering procedure which takes a gene out of one organism and placing it in another organism

Meiosis (condensed)

The parent cell must divide twice during meiosis, the first division creating 2 cells that are haploid. The second division seeing the 2 haploid cells each divide into 4 haploid cells.

DNA profiling

The process of matching an unknown sample of DNA with a known sample to see if they correspond

Meiosis

The process where a diploid cell creates four haploid gametes.

example of alleles

There are two alleles for earwax, one that is more dry (more common in Asia), and one that is more fluid (more common in Europe and Africa). This gene is also involved in the production of breast milk.

What happens when you only have one sickle cell allele?

Unlike most cases, when you have one allele for sickle cell disease and one normal allele, you have a slight amount of sickle cell disease (called sickle cell trait).

Gel electrophoresis

Used to separate fragments of DNA to identify its origin. Enzymes are used to chop up long filaments of DNA into varying sizes. The DNA fragments are placed into small holes in the gel, which are aligned along one end. The gel is exposed to an electric current, positive on one side and negative on the other. The effect is that the biggest and least charged particles do not move easily through the gel, so they get stuck close to the holes they were in at the beginning. The smallest and most charged particles pass through the gel to the other side with little difficulty. Intermediate particles are distributed in between. In the end, the fragments leave a banded pattern of DNA.

Polymerase Chain Reaction

Uses a machine called a thermocycler that takes a small quantity of DNA and copies all its nucleic acids to make millions of copies of the DNA.

Amniocentesis

Uses a needle to extract amniotic fluid which will contain cells.

Autoradiography

Uses radioactivity being given off by an object to create an image. Can be used to get images of DNA so its length can be measured.

Multiple alleles

Usually there are two versions of a gene, 2 alleles. When there are more than 2, it is considered multiple alleles.

Down Syndrome

When a child is born with 47 chromosomes instead of 46 because they have an extra chromosome 21.

Non-disjunction

When one or more pairs of homologous chromosomes fail to separate properly during meiosis.

Trisomy

When they are three chromosomes

Sex chromosomes

X and Y

What uses radioactivity to create an image of an object?

X-rays

Haploid

a cell that has 1 of each chromosome

Diploid

a cell that has 2 of each chromosome

gene

a heritable factor that consists of a length of DNA and influences a specific characteristic

karyogram

a picture of chromosomes

mutations

a random, rare change in genetic material

substitution mutation

a wrong base being substituted for the correct one, like in sickle cell disease

Dominant allele

allele that causes a phenotype whether with the same allele or a different one ex) Bb causes the B trait

Recessive allele

allele that effects the phenotype only when there are two of them ex) bb gives the recessive trait

How many genes do humans have?

an estimated 21,000 genes organized into chromosomes

cystic fibrosis

an inherited disease caused by a mutated gene on chromosome 7, where an excess amount of mucus is produced

Autosome

any chromosome that is not a sex chromosome

How are alleles created

by mutations

When does non-disjunction happen?

can happen during both Anaphases

Where is the gene for making transducin located?

chromosome 1

What is a defining feature of a species?

chromosome number

2n

diploid number

XX

female (gametes will all be X)

Examples of of completely sequenced organisms

fruit flies and E. coli

Are gametes haploid or diploid?

haploid

n

haploid number

Heterozygous

having two different alleles of a gene ex) Bb

Homozygous

having two identical alleles of a gene ex) BB, bb

When do plasmids reproduce?

independently of the cell

Carrier

individual with recessive allele that doesn't affect the phenotype

gene therapy

involves putting a good gene into someone who needs it, dangerous and has ethical issues

base changes

just one base change can create a mutation that causes disease

X chromosome

longer and contains more genes that the Y chromosome

XY

male (gametes will be X and Y)

Through which process can some individuals be born with less or more chromosomes?

non-disjunction

Genetically modified organisms

organisms that have had an artificial genetic change

Why do eukaryotes have two of every chromosome?

organisms that sexually reproduce receive one of each chromosome from each parent

Co-dominant alleles

pair of alleles tha tboth affect phenotype when heterozygous ex) RW make red and white

heritable

passed from parents to offspring ex) passing down hair or eye color

Locus

position of a gene on homologous chromosomes

Which organisms can have plasmids?

prokaryotes and archaea

Example of a cell without chromosomes

red blood cells

Homologous chromosomes

sets of two of the same chromosome (1 from mom and 1 from dad)

an example of a good mutation

some people are unable to contract HIV

Genotype

symbolic representation of a pair of alleles, typically two letters ex) Bb, GG, tt

How do nucleosomes help regulate the transcription process?

the areas of nucleosomes won't transcribe

genome

the complete set of an organisms base sequences, about 3 billion bases in humans

lactase

the enzyme that breaks down lactose, created by a mutation, thought to have originated in Europe

Who determines the sex of the child?

the male

karyotype

the specific number and appearance of the chromosomes of an individual

locus (plural loci)

the specific spot where a gene for a specific trait is always located

Why do prokaryotes only have one chromosome?

they reproduce by binary fission

How can we see if a cell has extra chromosomes from non-disjunction?

through a karyogram

Autosomal traits

traits that have their genes on one of the 22 pairs of autosomal chromosomes

Sex linked traits

traits that have their genes on one or both of the 2 sex chromosomes

Cairns' technique

uses radioactive material called radio markers. Radioactive form of Thymine using 3H. Used in 1962 to prove bacteria DNA is a loop.

alleles

variations or versions of a gene, usually different by only a few base pairs