Chapter 17 Flashcards by Safa Faisal

What is Inheritance?

Inheritance is the transmission of genes from generation to generation.

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What are Chromosomes?

Chromosomes are thread-like structures present in the nucleus of a cell.
- They are made of DNA, which contains genetic information in the form of genes.

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What is a gene?

A gene is a short length of DNA that codes for a protein.
- It is a section of the DNA strand, that contain instructions for making proteins.

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What is DNA?

DNA is Deoxyribonucleic acid.
- It is the molecule that contains instructions for growth and development of all organisms.
- DNA is found IN CHROMOSOMES.

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What is an Allele?

An Allele is another form of a gene.
They are variations of the same gene.
Ex: A gene is eye color, Alleles would be blue or brown.

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Describe inheritance based on sex chromosomes:

Normal body cells (somatic) contain 46 chromosomes, (diploid cells) 23 pairs.
- 1 pair, determines the sex of an individual; That is called the sex chromosomes.
- Males have XY
- Females have XX

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What is a Karyotype?

Karyotype is the outcome of chromosomes when scientists separate and arrange them according to size and appearance.

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How is sex determined?

Eggs cells all contain X chromosomes, Whereas the sperm cells may contain X or Y. (half carry X and half carry Y)
- If an X sperm fertilises the ovum/egg, the fetus will be female.
- If a Y sperm fertilises the ovum/egg, the fetus will be male.

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What is a Punette square?

It is a genetic diagram that demonstrates sex inheritance.
X X
X
Y

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What is the function of DNA?

DNA controls cell function by
controlling the production of proteins, including enzymes, membrane carriers and receptors for neurotransmitters.

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How do sequence of bases determine the protein?

The sequence of bases in a gene will determine the sequence of amino acids produced, that will make a specific protein.
- Different sequences of amino acids, result in different shapes of proteins.

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How is a protein made? (Protein Synthesis)

First, Messenger RNA (mRNA) copies the DNA base sequence in the nucleus and moves to the cytoplasm.
MRNA is a copy of a gene.
mRNA passes through Ribosomes.
Ribosomes use the mRNA strand to assemble amino acids into protein molecules.
The specific sequence of amino acids is
determined by the sequence of bases in the MRNA .

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What is mRNA?

Messenger RNA is a molecule used to copy and transfer information from the nucleus.
- mRNA is smaller than DNA
- It is made up of only 1 strand.
- It has base U (uracil)
- A, U, C, G

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What is Gene expression?

Some cells, have only specific proteins made in their cells.
- So genes which are needed to code for specific proteins are switched on/ EXPRESSED.
- Genes which are NOT needed are switched off.
* The expressed gene allows for the production of the specific protein.

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What is a Haploid nucleus?

It is a nucleus that contains a SINGLE SET of chromosomes. (one of each chromosome)
ex: egg and sperm cell

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What is a Diploid nucleus?

It is a nucleus that contains 2 SETS of chromosomes. (pairs)
ex: body cells

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What is Mitosis? Why is it important?

Mitosis is nuclear division that gives rise to genetically identical cells.
- This is important since cells wear out or get damaged, they have to be constantly replaced.

What is the role of Mitosis?

Mitosis plays an important role in:
- Growth
- Repair of damaged tissues for healing
- Replacement of old cells
- Asexual reproduction to reproduce offspring without fertilisation.

What happens in Mitosis?

Firstly, chromosomes duplicate into pairs before Mitosis.
- During Mitosis, the copies of chromosomes separate, maintaining the same chromosome number in each daughter cell.
- As a result, 2 genetically identical daughter cells are produced.
- One cell may become specialised, and stop dividing while the other continues to divide.

What is a stem cell?

A stem cell is an unspecialised cell thats divided by Mitosis to produced daughter cells that become specialised for specific functions.
ex: A zygote is first a fertilised egg cell, that divides after into different cell types.

What is Meiosis?

Meiosis is nuclear division that gives rise to cells that are genetically different.
- Meiosis is nuclear/Reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells.
- It is involved in production of gametes.

What are differences between Mitosis and Meiosis?

In Mitosis:
- 2 Daughter cells produced, Diploid.
- Genetically identical.
- One cell division occurs.
In Meiosis:
- 4 daughter cells produced, Haploid.
- Genetically different.
- Two cell divisions occur.

What are somatic cells?

Somatic cells are cells that are not involved in production of gametes.
Mitosis only takes place in Somatic cells.

IMPORTANT POINT:

Genes for everything are present in all cells.
However, only EXPRESSED genes allow cells to have specific proteins.

What is Genotype?

Genotype is the genetic makeup of an organism, including all its genes and alleles. Ex: Bb or BB

What is Phenotype?

*Pheno is Physical. Phenotype is the observable features of an organism; A feature we can see or find (ABO blood types) ex: Blue eyes

What does Homozygous mean?

Homo means same. - Homozygous is having two IDENTICAL alleles of a particular gene. ex: TT

What does Heterozygous mean?

Heterozygous means having two DIFFERENT alleles of a particular gene. ex: Tt

What is pure breeding?

Pure breeding is result of two identical homozygous individuals that breed together. - Heterozygous is not*

What is a Dominant Allele?

A dominant Allele is an Allele that is expressed if its present in the genotype. - Dominant is capital

What is a recessive Allele?

A recessive Allele is an Allele that is only expressed if theres NO DOMINANT ALLELE present in the genotype. - Recessive is lowercase

What is Monohybrid Inheritance?

It is the study of how a single trait/characteristic of an organism is passed from parents to offspring.

What does Homozygous recessive mean?

This means the genotype would be 2 identical recessive Alleles. ex: bb

What is a Test cross?

A test cross is used to identify an unknown genotype.

What is a Pedigree Diagram?

Pedigree Diagrams are used to track how a specific trait/disease is passed through generations. - They allow us to predict chances of inheriting the disease. - Females are circles - Males are squares

What is Codominance?

Codominance is a situation in which both alleles in heterozygous organisms contribute to the phenotype. *Is when both recessive alleles produce effects on an individual. NEITHER IS DOMINANT.* Ex: Blood groups

What is the Inheritance of Blood groups?

There are 3 Alleles for the gene; IA, IB and IO There are 4 blood types; A, B, AB, O - A and B are said to be Co-dominant. If a person inherits A and B, they will carry BOTH. - Group O have neither A nor B; O is not dominant over either A orB. so IaIo will still be A, and IbIo will still be B.

What is Sex Linkage (sex-linked characteristic)?

A sex-linked characteristic is a feature in which the gene responsible is located on a sex chromosome. - This makes it more common in one sex than in the other.

How come only X chromosomes carry genes that control characteristics?

This is because the X chromosome has longer arms on its chromatid. The male therefore, shows only 1 gene, (XaY) compared to female (XaXa)

How can a female be a carrier but not have the feature herself?

This is because a carrier female, has a dominant allele that masks effect of the recessive allele (carrying the disease) She may not have the disease herself, but its in her genotype, so she has a chance of passing onto offspring.