Genetics

IB Biology Genetics

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Florian Spiess

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Florian Spiess

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This flashcard set covers advanced topics in genetics, focusing on key concepts like chromosomes, alleles, and meiosis. It delves into processes such as crossing over, non-disjunction, and the stages of cell division, as well as genetic disorders like Down syndrome and sickle-cell anemia. The flashcards also explore mutations, their effects, and the structure of genes and genomes. Ideal for students and professionals in biology, this set provides a comprehensive overview of genetic principles and their applications in understanding hereditary traits and genetic diseases.

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Utilisateurs

Langue

Anglais

Catégorie

Biologie

Niveau

Autres

Créé / Mis à jour

11.03.2013 / 18.05.2018

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In meiosis what happens during anaphase two?

Sister chromatids are seperated and moved to opposite poles

In meiosis what happens in telophase two?

Complete haploid set of chromosomes at each pole; encapsulated in nuclear membrane

Nucleoli reform and cytokinesis occurs

What is non-disjunction?

When there is an error during meiosis, specifically at anaphase when homologous chromosomes don't seperate evenly

What is the problem caused by non-disjunction?

If a gamete is then involved in fertilisation the resultant individual has either 45 or 47 chromosomes, leading to a range of disorders

What is the cause of down syndrome?

3 chromosome 21's instead of 2

What are the effects of down syndrome?

Hearing loss

Visual disorders

mental and growth retardation

What is done to prevent down syndrome?

It is being tested for in expectant mothers

How is down syndrome tested for?

A maternal bood test records HCG (Human Chorionic Gonadotropin) and AFP (Alpha-fetoprotein) levels, chemicals released during pregnancy

A lower level of AFP and doubled level of HCG indicates a high chance of down syndrome

Further tests would then be carried out

How can chromosome abnormalities be confirmed?

Through a karyotype; an organised image of chromosomes at metaphase

Where can samples for a karyotype be taken from?

The amniotic fluid or placenta

What is the genotype?

The alleles of an organism

What is the phenotype?

The characteristics of an organism

What is a dominant allele?

An allele that has the same effect on the phenotype no matter if it is hetero- or homozygous

What is a recessive allele?

An allele that only has effect if it is present in homozygous state

What is a codominant allele?

Pairs of alleles that both affect the phenotype when in a heterozygote

What is the locus?

The specific region on the chromosome where the gene is found

Define homozygous

Having two identical alleles of a gene

Define heterozygous

Having two different alleles of a gene

What is a carrier?

A heterozygous individual bearing an unexpressed defective gene

What is a test cross?

Testing a suspected heterozygote by crossing it with a known homozygous recessive

What are eukaryote chromosomes made of?

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DNA and Proteins

What are the chromosome facts?

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1. The number of chromosomes per species is fixed

2. The shape of a chromosome is characteristic

3. The chromosomes of a cell occur in homologous pairs

4. Chromosomes hold the hereditary factors - genes

5. Chromosomes copy themselves

What is a gene?

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A heritable factor that controls a specific characteristic

What is an allele?

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One specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene

What is a genome?

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The whole of the genetic information of an organism

What is a homologous chromosome?

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Chromosomes that occur in diploid cells, comtaining the same sequence of genes, but have come from different parents

What is a sister chromatid?

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During interphase the DNA is replicated so a chromosome will have two identical sister chromatids when it enters cell division

How do mutations occur, and how can the chance of occurrence be increased?

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Mutations occur randomly, but the chance of occurrance can be increased by mutagens e.g. radiation, uv light and poisons

What do mutations affect?

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Transcription and translation

List two common mutation examples

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Substitution of bases

Base insertion and deletion causing frameshifts

What is the most common genetic disease and what does it do?

Sickle-cell anemia causes the haemoglobin molecules to stick together when in tissues of low oxygen concentration, which can lead to the blocking of capillaries

What type of process is meiosis?

Reduction division

In meiosis, what is the nucleus at the beginning and at the end?

Diploid nucleus (2n) --> haploid nucleus (n)

How many divisions does meiosis consist of?

What happenes to the parent cell during meiosis?

The one diploid parent cell divides into four genetically distinct haploid daughter cells

What occurs prior to meiosis?

Interphase

How much of meiotic division time is prophase one?

90%

In meiosis what happenes first during prophase one?

Chromosomes condense

Nuclear membrane breaks down

Nucleoli disappear

Spindle apparatus appears

In meiosis during prophase one, what happenes when the chromatids appear?

Homologous chromosomes come together and pair to form a BIVALENT

In meiosis during prophase one, how many chromatids does the bivalent have?

4 chromatids (2 from each chromosome)

1 / 50

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What is the genotype?

The alleles of an organism

What is the phenotype?

The characteristics of an organism

What is a dominant allele?

An allele that has the same effect on the phenotype no matter if it is hetero- or homozygous

What is a recessive allele?

An allele that only has effect if it is present in homozygous state

What is a codominant allele?

Pairs of alleles that both affect the phenotype when in a heterozygote

What is the locus?

The specific region on the chromosome where the gene is found

Define homozygous

Having two identical alleles of a gene

Define heterozygous

Having two different alleles of a gene

What is a carrier?

A heterozygous individual bearing an unexpressed defective gene

What is a test cross?

Testing a suspected heterozygote by crossing it with a known homozygous recessive

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