Ch.8 continuedCh.8 continued

Sexual reproductionSexual reproduction

What does the term What does the term homologous mean?homologous mean?

Same or same Same or same functionfunction

How many How many chromosomes are chromosomes are there in this picture?there in this picture?

2, 4 chromatids2, 4 chromatids

Are the versions (alleles) of the Are the versions (alleles) of the genes identical on homologous genes identical on homologous chromosomes?chromosomes?

Not necessarily, notice in the Not necessarily, notice in the picture the darker and lighter picture the darker and lighter version of the genes.version of the genes.

Are genes always at the same Are genes always at the same location (locus) on the location (locus) on the homologues?homologues?

Yes, Blue,green and purple are Yes, Blue,green and purple are always in the same locationalways in the same location

What do we call the chromosomes What do we call the chromosomes that are the same for both females that are the same for both females and males (1-22)?and males (1-22)?

AutosomesAutosomes The X and Y are called the _____ The X and Y are called the _____

chromosomeschromosomes Sex chromosomesSex chromosomes

What does diploid mean?What does diploid mean? The cell has two sets of The cell has two sets of

homolgous chromosomes, one homolgous chromosomes, one set from mom and one from set from mom and one from dad.dad.

What does haploid mean?What does haploid mean? One set of chromosomes.One set of chromosomes. What are the two types of What are the two types of

gametes produced during gametes produced during meiosis (sexual cell division) meiosis (sexual cell division) and are they haploid or diploid?and are they haploid or diploid?

Sperm and egg are haploidSperm and egg are haploid When do human cells become When do human cells become

diploid?diploid? After fertilization - sperm (23) After fertilization - sperm (23)

meets egg(23) = zygote (46)meets egg(23) = zygote (46)

The stages of meiosis are The stages of meiosis are different from mitosisdifferent from mitosis

When are the chromosomes When are the chromosomes duplicated?duplicated?

S phase of interphaseS phase of interphase What do you notice happening What do you notice happening

during prophase?during prophase? Crossing overCrossing over What do you think is happening What do you think is happening

during crossing over?during crossing over? Pieces of homologous Pieces of homologous

chromosomes are breaking off chromosomes are breaking off and exchangingand exchanging

How do the chromosomes line How do the chromosomes line up at the equator?up at the equator?

They line up as homologous They line up as homologous pairspairs

The stages of meiosisThe stages of meiosis

Unlike mitosis which Unlike mitosis which had 1 division, how had 1 division, how many divisions in many divisions in meiosis?meiosis?

22 How do the How do the

chromosomes line up chromosomes line up this time, in division this time, in division 2?2?

In a single file since In a single file since the homologous the homologous chromosomes were chromosomes were already separated.already separated.

What are some of the What are some of the differences between differences between mitosis and meiosis?mitosis and meiosis?

Mitosis Meiosis

1 division 2 divisions

Chromosomes line up at single file

Chromosomes line up as homologous pairs

Produces 2 identical diploid cells

Produces 4 different haploid cells

What is the difference between What is the difference between these two pictures?these two pictures?

Left both blues are on the left, Left both blues are on the left, right blue and red are on right blue and red are on opposite sidesopposite sides

How many different possibilites How many different possibilites for human combinations?for human combinations?

2223 23 = 8 million combinations = 8 million combinations with our 23 homologous with our 23 homologous chromosomeschromosomes

How does this show How does this show independent assortment?independent assortment?

Where the one set of Where the one set of chromosomes (large set) goes chromosomes (large set) goes has nothing to do with where has nothing to do with where the other set(Small set) goes.the other set(Small set) goes.

Independent assortmentIndependent assortment

More independent assortmentMore independent assortment

What type of What type of chromosomes are these?chromosomes are these?

HomologousHomologous How do we know they are How do we know they are

homologous?homologous? They have the same They have the same

genes, only the versions genes, only the versions are different.are different.

What versions of the What versions of the genes did the mouse on genes did the mouse on the right inherit?the right inherit?

The recessive white coat The recessive white coat and red eyes.and red eyes.

What about the mice on What about the mice on the left?the left?

We don’t know because We don’t know because they have the dominant they have the dominant traits theymay have the traits theymay have the recessive homologuos recessive homologuos chromosome as well.chromosome as well.

What is happening in What is happening in this picture?this picture?

Crossing overCrossing over What is the chiasma?What is the chiasma? The location where The location where

crossing over crossing over happens.happens.

How many different How many different combinations from combinations from crossing over?crossing over?

4, 2 the same as 4, 2 the same as original, 2 original, 2 recombinantsrecombinants

What process is being What process is being illustrated?illustrated?

KaryotypingKaryotyping

What is the sex of this What is the sex of this person?person?

FemaleFemale Do they have the normal Do they have the normal

number of number of chromosomes?chromosomes?

YesYes Are there any genetics Are there any genetics

problems?problems? You can’t tell from this You can’t tell from this

karyotypekaryotype

Is this a normal Is this a normal Karyotype?Karyotype?

No, one too many No, one too many chromosome 21s - chromosome 21s - Down’s SyndromeDown’s Syndrome

What does this graph What does this graph show?show?

As age of mother As age of mother increases the number increases the number of Down’s syndrome of Down’s syndrome births increasesbirths increases

When meiosis goes When meiosis goes wrong, what is it called?wrong, what is it called?

NondisjunctionNondisjunction What happened to the What happened to the

number of chromosomes number of chromosomes in each gamete?in each gamete?

Two have one too many, Two have one too many, two have one too few.two have one too few.

How many gametes are How many gametes are affected by affected by nondisjunction in meiosis nondisjunction in meiosis II?II?

Two, one has n+1 and Two, one has n+1 and one has n-1one has n-1

When the egg with too When the egg with too many is fertilized by a many is fertilized by a normal sperm the zygote normal sperm the zygote will have ___ extra will have ___ extra chromosome(s)chromosome(s)

11

What causes Klinefelter’s What causes Klinefelter’s syndrome?syndrome?

One or more extra X One or more extra X chromosomeschromosomes

Why might that cause Why might that cause infertility?infertility?

Mismatched Mismatched chromosomes cannot line chromosomes cannot line up correctly at metaphaseup correctly at metaphase

What is the sex of this What is the sex of this person?person?

Male with Klinefelter’s Male with Klinefelter’s syndromesyndrome

Which of the sex Which of the sex syndromes is most syndromes is most likely to happen?likely to happen?

MetafemaleMetafemale

X0 - Turner’s syndromeX0 - Turner’s syndrome

The fact that women The fact that women with Turner’s with Turner’s syndrome have heart syndrome have heart problems tells you problems tells you what about the X what about the X chromosome?chromosome?

There must be gene There must be gene on the X for heart on the X for heart formationformation

Which chromosomal Which chromosomal defect is the worst?defect is the worst?

A deletionA deletion Which defect is Which defect is

probably the least probably the least problematic?problematic?

InversionInversion

What is the Philadelphia What is the Philadelphia Chromosome?Chromosome?

When chromosome 22 When chromosome 22 has a piece of 9 - leading has a piece of 9 - leading to a type of leukemiato a type of leukemia

What causes Cri du What causes Cri du Chat?Chat?

A deletion on A deletion on chromosome 5chromosome 5

Gender testingGender testing