Genome Packing Chapter 12.5

two cells that are genetically identical to each other and to the parent cell.

mitosis

What is Meiosis?

type of cell division that reduces the chromosome number by half, creating four genetically unique haploid cells (gametes) like sperm and egg cells

What is Comparative genomics?

the study and comparison of genomes from different species

reveals conserved regions that help scientists infer evolutionary relationships and history.

What do Meiosis produce with half of the genetic content?

sex cells that are genetically different from each other and the parent cell.

What is a genome?

The genetic material of an organism in the nucleus.

DNA in the nucleus, and sometimes including DNA in organelles like mitochondria and chloroplasts

Difference between eukaryotic and prokaryotic DNA packing is that

DNA wraps around histones in eukaryote

Who uses mitosis and why?

unicellular eukaryotes (like protozoans and yeasts) for asexual reproduction.

Why is mitosis useful?

crucial for growth, tissue repair, and renewal.

What does diploid mean?

A cell will have two complete sets of chromosomes.

What is Binary Fission?

mitosis for prokaryotes (bacteria), which is how they reproduce.

What does haploid mean?

Cell having a single set of unpaired chromosomes.

What is Organismal Complexity?

refers to their hierarchical organization, with simpler organisms built from molecules and cells, and more complex ones adding layers of tissues, organs, and organ systems

Is there correlation between organism complexity and genome size or number of genes?

No

Do humans or the mustard plant have more protein-coding genes?

Mustard plant

How many base pairs is is one megabase?

One million

Do humans have larger or smaller genome size than amoebas and onions?

Smaller

What is the C-Value Paradox?

The disconnect between the complexity of an organism and the size of its genome

What can influence the size of a genome?

Number of chromosomes set

What is the majority category of genome?

Non-coding or unknown.

What are Alpha Satellites?

highly repetitive sequences located near the centromere.

Crucial for spindle attachment during cell division but do not contribute to protein-coding complexity.

What is the purpose of Transposable Elements (Transposons)?

DNA sequences that can replicate themselves and move to different locations within the genome.

What do DNA transposons do?

Replicate and transpose via replication and repair.

What are retrotransposons?

transpose using an RNA intermediate

Who discovered the transposons?

Barbra McClintock Nobel Prize in 1983

How much does a transposable make up of our genome?

Elements make up about 45%

What allows long DNA sequences to fit into the cell?

Supercoils

What is the purpose of supercoiling?

Allows all the base pairs to form, even though the molecule is underwound.

What mostly starts supercoiling?

Underwinding or negative supercoils

What is the function of transposable elements?

Their function is largely unclear, though they are thought to play a role in generating variability and thus evolution.

What is the issue with DNA sequences?

incredibly long and must be tightly packed to fit within a cell's nucleus (or the cell itself for prokaryotes).

How are negative supercoils created?

the DNA helix is twisted in the opposite direction (underwinding) by enzymes like topoisomerase during supercoiling.

Why are nucleosomes a fundamental packing unit in eukaroytes?

formed by DNA wrapping around a core of eight histone proteins.

What are histones?

highly conserved, positively charged proteins that bind tightly to the negatively charged phosphate groups of DNA.

What is the histone structure often called?

beads on a string

How is chromatin formed?

when nucleosomes are packed together into a denser fiber.

What happens to chromatin during cell divison?

further condenses into the familiar, compact chromosomes with the help of proteins called condensins.

When are chromosomes present?

Only form when cells are dividing.