Exam 3 Cell & Molecular

How do brain and kidney cells differ?

Brain and kidney cells possess identical genomes that express different proteins.

Which of the following statements about DNA synthesis on the lagging strand is false?

The double helix synthesized on the lagging strand contains short, permanent RNA sequences

What is mitosis?

Asexual cell division that results in 2 genetically identical daughter cells.

Bacteria divides by…

binary fission/asexual reproduction/mitosis

How many daughter cells arise from mitosis?

2

How many daghter cells arise from meiosis?

4

How can ecoli be different from each other if it comes from asexual reproduction?

they can Transfer dna from one organism to another.

Bacteria are always acquiring new..

genes

What are the 2 processes of Eukaryotic cell division?

Mitosis and Meiosis.

There are eukaryotic organisms that reproduce asexually. T/F

T

What is meiosis?

cell division or sexual reproduction. Provides four genetically distinct daughter cells.

What is the benefit of sexual reproduction?

Genetic variation in the offspring

You have 2 copies of chromosome 5, one from your father and one from your mother. What are they called?

Homologous chromosomes.

Are chromosomes large molecules?

Yes.

What helps to package chromosomes?

Proteins.

How many pairs of chromosomes do humans have?

23

Two copies of each chromosome and two copies of each gene means?

Diploid

One copy of each chromosome and gene is…

haploid.

Homologous chromosomes are the same size and contain the same genes but they have different…

DNA sequences.

Every humans chromosome 5 evolved from..

a common ancestor.

Homologous indicates that organisms are…

evolutionarily related

Homologous chromosomes

have the same genes but different DNA sequences.

What is a gene?

sequence of nucleic acids that encodes a protein or RNA molecule (info)

Alleles are…

different sequences of a gene.

We all have the same genes, but different..

sequences.

Races are a…

social concept.

When a chromosome is DNA replicated, its products are..

sister chromatids.

Sister chromatids have the same…

dna sequences

How are homologous chromosomes and sister chromatids different?

homologous chromosomes have different dna sequences and sister chromatids have the same.

How is sickle cell anemia created?

Some individuals have a different allele for the hemoglobin gene, which encodes the beta subunit of hemoglobin. If a person has two copies of this allele, they have sickle cell anemia.

Meiosis produces gametes fro sexual production. Are they haploid or diploid?

Haploid.

Sperm and egg are

one copy of each chromosome and are gentically distinct from one another

when a sperm and egg fuse they create a…

zygote

22 of the 23 pairs of chromosomes in humans are referred to as..

autosomes

Autosomes are…

non sex chromosomes.

The 23rd pair of chromosomes are called..

sex chromosomes.

Which chromosome is larger? X or Y?

X

Which chromosome has more genes?

X

A human with 2 x chromosomes will develop as a…

Female

Individual with an x and y chromosome develops as a…

male

In mammals, the presence of the y chromosome leads to…

male development

An individual who is XY developing as a female is referred to as..

Sexually reversed.

Chromosomes have genes and the genes encode the…

proteins.

There are very few genes on which chromosome?

Y

what is the SRY gene?

A gene present on the Y chromosome. it encodes DNA binding protein that regulates gene expression.

If the SRY gene is expressed, it leads to..

Male development.

How can you have a female with two x chromosomes develop as a male?

A part of the fathers SRY gene from his chromosome broke off and attached to another chromosome.

Why is the Y chromosome so much smaller than the X chromosome?

At some point during evolution mammals evolved so that sex determination would be based on the SRY gene. The Y chromosome has the SRY gene. over mammalian evolutionary history, dna would be lost from the Y chromosome(reversions/deletions).

what is the purpose of the y chromosome being so small

It prevents the exchange between the x and y chromosome of dna in meiosis.

In autosomes, the alleles are…

swapped from one to the other, creating genetic variation.

What is the purpose of meiosis?

To produce gametes for sexual reproduction

What are the products of meisosis?

Four genetically unique haploid daughter cells

Meiosis starts with what type of cell?

Diploid parental cell

After DNA replication, a replicated chromosome consists of two…

sister chromatids.

a human genome has how many chromosomes?

23

A human genome has how many base pairs of dna?

3 billion

How many genes does a human genome have?

20000

Where are the genes from the genome distributed?

The chromosomes

A gamete is a mix of…

dna sequences from both parents

Interphase is not a part of…

mitosis and meiosis

When cells are not dividing, they are in…

interphase

In interphase, the chromosomes..

are dispersed (not condensed)

When chromosomes are dispersed, genes are…

being expressed. (so that the proteins that they encode can occur)

When does DNA replication occur?

Interphase

Prior to meisosis…

chromosomes are replicated in interphase

When meisosis starts…

dna replication has already occurred

The centromere is the site where…

the sister chromatids are attached

meisosis i is…

the first round of cell division

What carries out all steps of meisosis?

Proteins

The first stage of meiosis is…

Prophase I

Prophase I is

The first step of Meiosis, where genetic variation is created

What is the first thing that happens is prophase I

The chromosomes condense (become more compact), which stops gene expression (can be seen under microscope)

What is the second thing that happens is prophase I

Homologous chromosomes align (pair up)

What is a tetrad?

A pairing of homologous chromosomes

What is four double helices?

a tetrad

What happens after homologous chromosomes align?

Crossing over occurs.

What is crossing over?

An physical exchange of DNA between homologous chromosomes.

What do proteins do during crossing over?

mediate exchanges of DNA

What is the result of crossing over (IMPORTANT FOR ESSAY QUESTION)

New combinations of DNA sequences with maternal and paternal alleles

After crossing over, what happens?

Homologous chromosomes separate a little bit (creating space)

What is the second stage of Meiosis I?

metaphase I

What happens during metaphase?

proteins called microtubules move tetrads to the equator of the cell. They are randomly aligned

What is the third stage of meiosis?

Anaphase I

What happens during anaphase I?

homologous chromosomes are pulled to opposite ends of the cells. they are separated randomly

What is the second stage where creating genetic variation occurs?

Anaphase I

What is the random alignment and separation of chromosomes called?

Independent assortment

Alignment happens in…

Metaphase

Separation happens in…

Anaphase

How does genetic variation occur during meisosis?

Crossing over and independent assortment.

What is the fourth stage of meisosis?

Telophase I

what happens during telophase I?

the completion of cell division.

What is cytokinesis?

A division of the cytoplasm

After cell division is complete, what are the products?

Two genetically distinct daughter cells, with one copy of the sister chromatids from each chromosome

What is Meiosis II?

Cell division without DNA replication

What is the result of Meiosis II?

two more daughter cells, totaling 4.

the molecules that undergo crossing over and independent assortment are:

homologous chromosomes

what is nondisjunction?

a mistake that happens in meiosis where chromosomes are not separated properly.

What is the usualy result of nondisjunction?

Aneuploidy. All gametes having either an extra or missing chromosome.

Why do we only see aneuploidy for chromosome 21 and the sex chromosomes.

Nondisjunction for the other chromosomes is lethal for the developing embryo.

Why is an abnormal chromosome number usually lethal to the developing fetus

The incorrect amounts of proteins are made from the missing or extra chromosome. genes encode proteins, uses too many.