Life Science - Genetics and Inheritance

What is Genetics?

the study of heredity

What is a Gene?

A unit of inheritance; a segment of DNA that codes for a specific characteristic or enzyme.

What is an Allele?

Different forms or versions of the same gene, found at the same position (locus) on homologous chromosomes.

What is a Genotype?

genetic makeup of an organism

What is a Phenotype?

physical characteristics of an organism

What does Homozygous mean?

Having identical alleles for a specific gene

What does Heterozygous mean?

Having different alleles for a specific gene

What is a Dominant Allele?

An allele that masks the effect of a recessive allele

What is a Recessive Allele?

An allele that is only expressed when in the homozygous state

What is a Monohybrid Cross?

A genetic cross that studies the inheritance of a single trait controlled by one gene.

What is a Dihybrid Cross?

a cross that examines the inheritance of two different traits

What are Somatic Cells?

body cells, diploid

What are sex cells

gametes, haploid

What is Complete Dominance?

When one allele completely masks the expression of another

What is Co-dominance?

When both alleles are fully expressed in the phenotype (e.g., AB blood type).

What is Incomplete Dominance?

When the phenotype is a blend of both alleles (e.g., red and white flowers produce pink).

What is Polygenic Inheritance?

Characteristics that are influenced by more than one gene

What are Sex-Linked Characteristics?

Traits associated with genes found only on the X chromosome

What is a Karyotype?

The number and visual appearance of chromosomes in a cell nucleus.

What is a Locus?

Location of a gene on a chromosome

What is Chromatin?

uncoiled DNA that condenses to form chromosomes

What is a Chromosome?

a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

What is an auto some?

chromosome that is not sex linked

How many autosomes do humans have?

22 pairs

What is a gonosome?

sex chromosome

What is our gonosome

23rd pair of chromosomes

Who is Gregor Mendel and what did he do?

Gregor Mendel was a botanist who studied pea plants. He discovered that you get one gene from each parent and studied dominant/recessive traits.

What is the law of dominance?

If 1 of 2 alleles is dominant then the dominant trait will be expressed in the phenotype whereas the other receive allele will be masked.

Mendal's Law of Segregation

an organism possesses two factors which separate or segregate so that each gamete contains only one of these factors

homologous chromosomes

Pair of chromosomes that are the same size, same appearance and same genes.

Blood types are what type of dominance

Co-dominance

Blood group O genotype

II

Blood group AB genotype

IAIB

Blood Group A genotype

IAIA or IAi

Blood Group B genotype

IBIB or IBi

Antigens

Substances that can trigger an immune response

Makes have ____ chromosomes

XY

females have ____ chromosomes

XX

The probability of offspring being male of female is…

50%

Difference between X and Y chromosome

Y chromosomes are shorter (carry few genes) and X chromosomes are larger(carry more genes)

Why do sex-linked genetic diseases occur more often in males?

Males only have one X chromosome, so a recessive allele on it will always be expressed (no corresponding allele on the Y to mask it).

Why are females less likely to have sex-linked diseases?

Females have two X chromosomes; a normal dominant allele on one X can mask the recessive allele on the other. They can be carriers instead.

How is colour blindness inherited?

It is a sex-linked recessive disorder due to a defect in the red or green cones of the eye.

What is haemophilia?

A recessive sex-linked disorder(x chromosome) where the blood cannot clot properly due to missing clotting factors.

What is a haemophilia carrier?

A female who has one recessive haemophilia allele and one normal allele; she does not have the disease but can pass it on.

What is a gene mutation?

change in DNA sequence

What is a chromosomal mutation?

A change in the number or structure of chromosomes

Causes of mutations

Copying Errors
• Incorrect copying of the DNA sequence
•Exposure to Chemicals & UV radiation
Carcinogens
Viruses

Harmless mutation

Mutation with no effect on organism's function.

Harmful mutation

Mutations that do affect the functioning of the body causing a harmful condition

lethal mutation

a gene or chromosomal mutation that influences the development of an organism in such a way that the organism cannot survive

Variations of species may be a result of

meiosis, reproduction and mutations

gene mutation examples

Colour blindness and Hemophilia

Chromosomal mutation example

Down syndrome

Klinefelter syndrome

A chromosomal disorder in which males have an extra X chromosome, making them XXY instead of XY.

sickle cell anemia

a autosomal co-dominant genetic disorder that causes abnormal hemoglobin, resulting in some red blood cells assuming an abnormal sickle shape

What is the symptom of the sickle cell?

Reduced surface area to absorb oxygen

Albinism

a genetic condition characterized by a deficiency or the absence of pigment in the skin, hair, and irises of the eyes

Genetic lineage/pedigree

A genetic lineage/pedigree traces the inheritance of characteristics over many generations.

Biotechnology

use and application of living things and biological processes to improve the quality of human life

Genetics engineering includes

Stem cell research, genetically modified organisms, cloning

What are stem cells?

unspecialized cells from which differentiated cells develop

Types of stem cells

embryonic and adult

Sources of stem cells

• umbilical cord and placental stem cells
• embryonic stem cells
• adult stem cells

Uses of stem cells

replacing damaged cells/organ replacement,skin regeneration/growing skin tissue, growing nerve cells to treat brain disorders

GMO or transgenic organisms

organism that contains genes from other organisms

Recombinant DNA

DNA that has been formed artificially by combining constituents from different organisms.

How scientists use recombinant DNA (inserting the human gene for insulin into bacteria)

1. Remove plasmid from E. coli
2. Use restriction enzyme to cut open plasmid
3. Use enzyme to cut out gene for insulin in human pancreatic cells
4. Add insulin gene into plasmid to make recombinant DNA
5. Return recombinant DNA to E. coli
6. E. coli accepts it and starts to produce insulin

Uses of GMOs

to breed more productive crops/animals to increase yield

to produce drugs or hormones (e.g. insulin)

to 'infect' cells to cure diseases (gene therapy)

Benefits of genetic modification in agriculture

1. Increased food production and crop yields
2. Improved health of humans, less dependence of medicines
3. Decreased use of pesticides, herbicides
4. Greater nutritional value
5. Extended shelf life

Bt gene

A gene inside bacterium, responsible for producing a toxin that kills common corn pests.

Carotene production gene use

used in rice to increase vitamin a content

Cloning

The process of producing genetically identical individuals through non-sexual means.

Benefits of cloning

replace damaged tissue e.g. skin, heart

Genetic diseases could be prevented.

improve food supply and quality.

Reproductive cloning process

1. Take out surrogate egg cell
   2.Remove nucleus so that the egg cell remains
2. Take body cell from champion cow
3. Remove nucleas of body cell from champion cow and combine with empty egg cell
4. Use electric currentto stim egg cell to start dividing forming an embryo
5. Embryo put into surrogate cow

What is mitochondrial DNA (mtDNA)?

DNA found in the mitochondria

How is mtDNA inherited?

from the mother

Why is mtDNA useful for tracing inheritance?

It doesn't recombine, so it stays the same through the maternal line

What is DNA fingerprinting?

A process that uses unique non-coding sequences of DNA, cut and separated by electrophoresis, to produce a band pattern unique to each person.

What are some uses of DNA fingerprinting?

paternity test, maternity tests, and crime scenes