BS1050 Block 1 - Rules of inheritance

What is a chromosome?

A colored body that contains one duplicated chromosome, consisting of two chromatids and a centromere.

What are telomeres?

Structures at the ends of chromosomes that protect them from deterioration.

What is chromatin?

A complex of DNA, proteins, and enzymes that package DNA into the cell nucleus.

What does 'n' represent in genetics?

The number of chromosomes in a haploid cell.

What is the haploid number of chromosomes in humans?

n = 23.

What does '2n' signify?

Diploid, indicating two copies of each chromosome type, one from each parent.

What is the diploid number of chromosomes in humans?

2n = 46.

What is the significance of the Human Genome Project?

It aimed to sequence and map all the genes of Homo sapiens, completed in April 2003.

What is the total size of the human haploid genome?

3,300 Mb or 3.3 Gb.

What is the expected number of protein-coding genes in the human genome?

>100,000 protein-coding genes.

What is 'junk DNA'?

The vast majority of the genome that has no known function.

What happens to DNA content during the S phase of the cell cycle?

DNA content rises from 2c to 4c as DNA is replicated.

What is the DNA content of a haploid, unreplicated cell represented by?

The symbol 'c'.

What are autosomes?

Chromosomes that look the same in both males and females, excluding sex chromosomes.

What are sex chromosomes in humans?

The 23rd pair of chromosomes, with females having XX and males having XY.

What is the function of transcription factors?

Proteins that help initiate and regulate the transcription of genes.

What is the relationship between genome size and organism complexity?

There is no direct correlation between genome size (n) and the complexity of the organism.

Who announced the intention to sequence the human genome in 1998?

J. Craig Venter of Celera Genomics.

What is the structure of a duplicated chromosome?

It consists of two chromatids, a centromere, and telomeres.

What is the role of DNA and RNA polymerases?

Enzymes that synthesize DNA and RNA during replication and transcription.

What does '3n' signify in genetics?

Triploid, indicating three copies of each chromosome type.

What is the function of DNA-metabolizing enzymes?

Enzymes involved in the processes of DNA replication and repair.

What is the ENCODE Project?

A research initiative started in 2003 to analyze the human genome and its functions.

What was the focus of the ENCODE Pilot Project?

It focused on 1% of the human genome.

How many protein-coding genes are estimated in the human genome?

Approximately 21,000 protein-coding genes.

What percentage of the human genome is involved in gene regulation?

About 80% of the genome.

What did the ENCODE Project reveal about 'junk DNA'?

It provided evidence that much of the genome previously considered 'junk DNA' is functionally important.

How long is the human genome when fully extended?

Approximately 1 meter long.

How many chromosomes are in a human cell?

46 chromosomes.

What is the approximate length of DNA packaged into human chromosomes?

About 2 meters of double-stranded DNA.

What modifications can occur on histone tails?

histone tails- jammed in nucleosome small aa tail sticks out- acts like a sticky tab on what to do with that section of dna

(To keep it organized in the "library" (the nucleus), you would:

1. Wrap the ribbon around spools (Histones).

2. Group those spools together to form a chapter (Nucleosome).

3. Stack those chapters onto a shelf (Chromosome)

Acetylation, methylation, phosphorylation, and ubiquitination.

What is the significance of histone tail modifications?

They can alter chromatin structure and influence gene expression.

What does the 4D Nucleome program aim to study?

The three-dimensional organization of the nucleus in space and time.

What are the phases of the ENCODE Project?

ENCODE Pilot Project, ENCODE 2, ENCODE 3, and ENCODE 4.

What is the role of chromatin-binding proteins?

They interact with DNA and histones to regulate gene expression and chromatin structure.

What is the approximate length of DNA wrapped around a nucleosome?

Approximately 147 base pairs.

What is the role of barrier elements in chromatin?

They block the spread of heterochromatin and maintain euchromatic regions.

What is the significance of the modENCODE Project?

It focused on identifying functional elements and regulatory circuits in Drosophila.

What are the nine states of Drosophila chromatin?

States include transcription start sites, transcript elongation, regulatory regions, and various types of heterochromatin.

What is the function of HP1 protein in heterochromatin?

It binds to K9-methylated nucleosomes and recruits enzymes that spread the inactive state.

What are the main components of the human genome?

Protein-coding genes, noncoding RNAs, regulatory elements, and repetitive sequences.

What is the significance of the 4D Nucleome program's second phase?

It focuses on understanding chromatin dynamics and their implications for human health and disease.

What is a eukaryote?

An organism with a true nucleus.

What does diploid mean?

Having two copies of each gene (one from each parent).

What does haploid refer to?

Having one copy of each gene (as in gametes).

Define a gene.

A fragment of DNA that encodes RNA.

What are alleles?

Alternative forms of the same gene.

What are homologous genes?

Copies related by descent; the same gene in different species.

What is the difference between homologous and orthologous genes?

Homologous genes are related by descent, while orthologous genes are homologous genes in different species.

What is a homozygote?

An organism with two identical alleles for a specific gene.

What is a heterozygote?

An organism with two different alleles for a specific gene.

What is a phenotype?

The observable form or characteristics of an organism.

What is a genotype?

The specific allele composition of an organism.

What is a haplotype?

DNA variations that tend to be inherited together.

What is incomplete dominance?

When the heterozygous phenotype is intermediate between the two homozygous phenotypes.

What is codominance?

When both alleles in a heterozygote contribute equally to the phenotype.

What is the ABO blood group system?

A system with four phenotypes (A, B, AB, O) determined by the presence of antigens A and B.

What is the gene responsible for the ABO blood group?

Gene I, which encodes a glycosyltransferase.

What is achondroplasia?

A genetic disorder causing the most common type of dwarfism, inherited as an autosomal dominant trait.

What mutation causes achondroplasia?

A mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene.

What is Huntington's disease?

A late-onset neurodegenerative disorder caused by CAG repeat expansions in a gene.

What is epistasis?

Gene interactions that affect the phenotype, where one allele masks or modifies the effects of another.

What is incomplete penetrance?

When a particular allele results in a defined phenotype in some but not all individuals.

What is expressivity?

The degree to which a genotype is expressed in an individual's phenotype.

What is the heterozygote advantage?

When heterozygous individuals have a greater fitness than either homozygous group.

How does sickle-cell trait provide protection against malaria?

Individuals with sickle-cell trait are less susceptible to malaria.

What is balancing selection?

A process that maintains multiple alleles in a population at frequencies higher than expected by mutation alone.

What is the significance of the β-globin gene in sickle-cell disease?

The mutation in the β-globin gene causes sickle-cell anemia, which is influenced by oxygen levels.

What is the difference between dominant and recessive alleles?

Dominant alleles express their traits in heterozygotes, while recessive alleles do not.

Who is considered the founder of Transmission Genetics?

Gregor Mendel

What plant did Mendel use as a model system for his experiments?

Pea plants

What are the characteristics of the pea plants used by Mendel?

Annual, highly productive, many traits, hermaphrodite flowers, capable of self- and cross-fertilization

What is the significance of Mendel's approach to genetics?

It was model system based, reductionist, and quantitative.

What does Mendel's First Law state?

In a diploid organism, the two copies of a gene segregate during meiosis.

What is the expected phenotypic ratio in the F2 generation of a monohybrid cross?

3:1 (dominant to recessive traits)

What does the term 'allele' refer to?

Different forms of a gene that can exist at a specific locus.

What does Mendel's Second Law of Independent Assortment state?

During gamete formation, alleles of independent genes assort randomly.

What is the expected phenotypic ratio in the F2 generation of a dihybrid cross?

9:3:3:1

What is the difference between dominant and recessive alleles?

Dominant alleles mask the expression of recessive alleles in heterozygotes.

What notation is used for dominant and recessive alleles?

Typically, uppercase letters represent dominant alleles (e.g., R), and lowercase letters represent recessive alleles (e.g., r).

What is a pure breeding strain?

A strain that consistently produces offspring with the same phenotype when self-fertilized.

What does the term 'genotype' refer to?

The genetic constitution of an organism, represented by the alleles it possesses.

What does the term 'phenotype' refer to?

The observable physical or biochemical characteristics of an organism.

What is the significance of the F1 generation in Mendelian genetics?

The F1 generation is the first filial generation, produced by crossing two parental strains.

What is the expected genotypic ratio in the F2 generation of a monohybrid cross?

1:2:1 (homozygous dominant: heterozygous: homozygous recessive)

What is meant by 'complementation' in genetics?

The phenomenon where two different mutations in the same gene can lead to a normal phenotype when present in a heterozygote.

How does probability theory relate to Mendelian genetics?

It helps predict the likelihood of obtaining specific genotypes and phenotypes from genetic crosses.

What is the role of gametes in Mendelian genetics?

Gametes carry alleles that combine during fertilization to form the genotype of the offspring.

What is the relationship between genes and chromosomes?

Genes are segments of DNA located on chromosomes, and they are the basic units of inheritance.

What does the term 'hermaphrodite' mean in the context of pea plants?

It refers to plants that have both male and female reproductive organs, allowing self-fertilization.

What is the significance of the 2x2 probability calculation in Mendelian genetics?

It illustrates how two events (gametes) can produce four possible outcomes in a monohybrid cross.

What is the expected outcome of crossing two heterozygous round pea plants (Rr)?

The expected genotypic ratio is 1 RR : 2 Rr : 1 rr, and the phenotypic ratio is 3 round : 1 wrinkled.

What is the expected outcome of a dihybrid cross between two heterozygous plants (RrYy)?

The expected phenotypic ratio is 9 round yellow : 3 round green : 3 wrinkled yellow : 1 wrinkled green.

What does 'self-fertilization' mean?

It refers to the process where a plant's own pollen fertilizes its ovules.

What is the importance of using a model organism like the pea plant in genetics?

Model organisms allow for controlled experiments and clear observation of inheritance patterns.

What are the two processes discussed in the lecture that relate to genetic variation?

Mitosis and Meiosis

What type of cells are produced by mitosis?

Two diploid, genetically identical somatic cells

What is the genetic information status of somatic cells?

Diploid, identical genetic information

What is the genetic information status of gametes?

Haploid, variable genetic information

What occurs during the Leptotene stage - first stag of prophase of meiosis?

Chromosomes start to condense.