Get Nerdy with Judy Scher

It’s just plain fascinating to nerds like me!!!

This is a BIG area of research now

See articles in magazines like “American Bee Journal” on bee genetics

and may hear future speakers talk about this in conventions.

Helps to appreciate the challenges in breeding bees for selective traits

Fast review of chromosomes and genes

Epigenetics: What makes a queen and not a worker

Haplodiploidy in Hymenoptera

Mixing of the honey bee gene pool

Recombination of genes

Promiscuity of queen

Sex alleles: What makes “femaleness/maleness” in honey bees?

DNA structure (nucleotide pairs)

Mitosis (cell division)

Genes involved in hygienic traits

Selective breeding for certain traits

Cape bees (thelytoky)

(hey!...we only have 40 minutes!!!)

Genes located on Chromosomes in the cells

Each chromosome is composed of loooong strand of DNA

DNA contains all the genetic information of an organism

e.g.. the gene that codes for producing the protein insulin

Location of the gene on the chromosome is a Locus (plural is Loci)

Different expressions of the same gene are alleles (e.g.. brunette or blonde or red hair)

Dominant vs Recessive Traits

Heterozygous alleles Same gene with small differences in DNA

One may be Dominant and the other Recessive.

Example: Gene for brown eyes is dominant to gene for blue eyes

Homozygous alleles Same gene with identical DNA

2 recessive genes will be expressed in this case because there

is no dominant gene.

Diploid vs Haploid

All FEMALE hymenoptera are Diploid

Chromosomes are paired: 1 mother + 1 father

Queen and Worker

Have complete genetic material 50% from their mother, 50% from father.

Homologous Chromosomes

Haploid # A. mellifera =16 16 pairs of chromosomes in female

Diploid # A. mellifera = 32

Cells of DRONES (all hymenoptera males) are Haploid

Chromosomes are NOT paired.

Drones receive ONE set of chromosomes from the unfertilized egg

Cells have the haploid # of 16 chromosomes

The Drone:

Does not have father, but has a grandfather

Does not have sons, but has grandsons

I lied! There is one type of cell in all females that must be haploid

– THE EGG

Gametes are the egg and sperm

produced in the ovaries and testis by MEIOSIS – 2 special divisions of the cell

1’st results in 2 haploid cells (females)

2’nd like mitosis – results in 4 cells (females), 2 cells (drones)

Reduction of chromosomes by half from diploid to haploid

So the union of egg and sperm results in an organism with a diploid set of

chromosomes - not multiples!!!

Very important to maintain a good gene pool

Mixing the genes results in “hybrid vigor”

Less mixing results in poor genetic variability (inbreeding) and more lethal genes

In North America the A. mellifera gene pool is limited

A. mellifera has very few queen breeding operations

We can’t import bees from other countries

A gene pool is the collection of all the genes of a population within a species.

e.g.. The population of A. mellifera in Canada and the US.

The sum of all the alleles at all the loci.

In the first phase of meiosis CROSSING OVER of chromosome pairs

- resulting in even more mixing of genes.

In A. Mellifera meiotic cross-over areas are greater than any other animal studied.

40x more than in humans!! Kudos to the female bee!!!!!

Meiosis (in female hymenoptera) results in mixing of genes

half from father, half from mother

keeps variability in the gene pool

Interphase DNA

replicates

Prophase I Crossing Over

(Recombination)

Tetrads of homologous

chromosomes

X-over at non gene areas

Metaphase I: Pairs line up

Spindles attached

Anaphase I Homologous pairs

separated

Telophase I nuclear membrane forms

Cytokinesis takes place

Formation of 2 haploid

cells

Prophase II

Metaphase II

Anaphase II

Telophase II

4 haploid cells all genetically different

(poor drones getting ANOTHER bad rap)

Meiosis in the honey bee drone is incomplete. “Meiosis Interruptus”

The sperm are identical.

No mixing of the gene pool in the drone!!!

In the first division the process is confused!

But still goes on to a second division to produce germ cells which will divide

and become sperm.

Meiosis I

Meiotic apparatus “blebbed” off cell

No spindles attach to chromosomes

Incomplete division

Cell divides as in Meiosis II

2 identical cells will develop into sperm

Promiscuity of the virgin queen leads to more genetic variability

Queens may mate with up to 20 drones

A well mated queen is recognized by the workers:

Queen puts out more queen pheromone

Better retinue

Less chance of supercedure.

CAVEAT: if breeding to select a certain trait, drones need to all have that trait.

Leads to less variability

There are no sex chromosomes in honey bees like there are in animals.

Mammals have one unmatched pair of chromosomes XX = female Xy = male

In bee there is a key gene governs sex determination

csd “complementary sex determiner

gene is on one locus on one chromosome

csd has around 19 different alleles: Expression of the same gene

.......................

This csd gene is expressed in the embryo in the egg at 12 hours

It has been mapped to chromosome # 8 and the DNA has been sequenced

The paired chromosomes MUST be heterozygous to result in a FEMALE The queen fertilizes an egg with sperm of a different allele

These pairs, for example will result in a female bee

The unfertilized egg only has one chromosome # 8 and ALWAYS results in a

drone

This HOMOZYGOUS pair will result in a DIPLOID

DRONE (2 genetically identical csd genes)

Source: Glenn Apiaries http://www.glenn-apiaries.com/genetics.html#anchor1561346

Diploid drone eggs hatch, produce a pheromone which

tells workers to destroy the larva

This is what results from inbreeding

Breeding for a certain trait can produce this

Since queens are fertilized by an assortment of drones in a big DCA

this is uncommon

Also queens go to a different DCA than their brothers!

Epigenetics

Something from the environment that causes a direct change

in the DNA which affects gene expression.

Until recently thought to be the substance

which caused the queen to become a queen!

Royal jelly (nope)

Fed to Queen entire life

Fed to worker larvae up to 96 hours (worker jelly very similar to royal jelly)

Produced by nurse bees in hypopharyngeal glands

Extremely nutritional, high protein, etc.

Researchers studying the immune response bees obtain by consuming

certain chemicals in pollen and honey.

p-coumeric acid (and other phenolics)

Help plants discourage plant-eating insects

Found in pollen and honey

Helps workers detox pesticides faster

**Bee bread (fermented pollen and honey) contains

p-coumeric acid and fed to workers starting at 96 hours!

Increases immune response in adult bees

Serendipity In Research!!

Researchers found that :

Workers developed increased growth in ovaries at 96 hours!

This is irreversible!

When workers fed p-coumeric acid

When p-coumeric acid was NOT fed to workers

Workers had ovaries <<<< in size than queens

(which is normal)

But there may be many other chemicals which regulate her development

In bees NOT fed p-coumeric acid

Researchers found 14 genes involved in queen/worker differentiation

were “upregulated” or “expression” increased

When fed p-coumeric acid

In nature Queen NEVER fed pollen or honey therefore NEVER receives

p-coumeric acid in her life

50% of genes involved in organ size were significantly changed in

gene expression.

At 96 hours workers get their first taste of bee bread and p-coumeric acid

This is the point of no return!!

The End

Photo by Judy Scher